Methods and apparatus for transmitting and receiving uplink control information and for requesting random access in wireless communication system

ABSTRACT

The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system such as Long Term Evolution (LTE). The present disclosure provides a method for transmitting uplink control information, including: determining, by a user equipment (UE), at least two carriers for uplink transmission in a cell currently connected by the UE, and determining a carrier for uplink control information (UCI) transmission from the at least two carriers for uplink transmission; determining, by the UE, a relative frequency-domain position and a time-domain starting position occupied by UCI on the determined carrier for UCI transmission; and retuning, by the UE, a center radio frequency of the UE to a center frequency of the carrier for UCI transmission, and transmitting the UCI according to the relative frequency-domain position and the time-domain starting position occupied by the UCI; in which, the UE receives and transmits information on one carrier at one time. Using the present disclosure can efficiently transmit UCI. The present disclosure further discloses a method for requesting random access, which comprising steps of: determining a time division duplex (TDD) uplink time-domain resource; determining, according to the TDD uplink time-domain resource, a time-domain resource used for transmitting a narrowband physical random access channel (NPRACH); determining a time-domain format for an NPRACH transmission group, the time-domain format comprising: one NPRACH transmission group comprises at least two transmission units which are discontinuous in time domain, and one transmission unit comprises one or more NPRACH symbol groups which are continuous in time domain; and, determine time-domain resource used for transmitting NPRACH to transmit an NPRACH transmission group in the time-domain format. Compared with the prior art, in the present disclosure, a time-domain position for transmitting an NPRACH is designed according to the characteristics of TDD uplink time-domain resource, so that a random access process can be deployed within an LTE band or an LTE guard band; moreover, since an NB-IoT communication system based on TDD is used, a higher utilization rate of system spectrum resources is achieved.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 16/636,803, filed on Feb. 5, 2020, which is a U.S. National Stageapplication under 35 U.S.C. § 371 of an International application numberPCT/KR2018/009010, filed on Aug. 8, 2018, which is based on and claimspriority of a Chinese patent application number 201710670026.0, filed onAug. 8, 2017, in the Chinese Patent Office, of a Chinese patentapplication number 201710681936.9, filed on Aug. 10, 2017, in theChinese Patent Office, of a Chinese patent application number201711137954.7, filed on Nov. 16, 2017, in the Chinese Patent Office,and of a Chinese patent application number 201810078508.1, filed on Jan.26, 2018, in the Chinese Patent Office, the disclosure of each of whichis incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure relates to radio communications, and inparticular to methods and apparatus for transmitting and receivinguplink control information and for requesting random access.

BACKGROUND ART

To meet the demand for wireless data traffic having increased sincedeployment of 4th generation (4G) communication systems, efforts havebeen made to develop an improved 5th generation (5G) or pre-5Gcommunication system. Therefore, the 5G or pre-5G communication systemis also called a ‘Beyond 4G Network’ or a ‘Post Long Term Evolution(LTE) System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid frequency shift keying (FSK) and quadratureamplitude modulation (FQAM) and sliding window superposition coding(SWSC) as an advanced coding modulation (ACM), and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse codemultiple access (SCMA) as an advanced access technology have beendeveloped.

DISCLOSURE OF INVENTION Technical Problem

The present disclosure provides methods and apparatus for transmittinguplink control information, so as to improve the uplink data rate, andefficiently perform uplink control information (UCI) transmission,especially for narrowband systems that operate in a time division duplex(TDD) frequency band and a frequency division duplex (FDD) frequencyband.

Solution to Problem

To achieve the above object, the present disclosure provides thefollowing technical solutions as below.

A method for transmitting uplink control information, including,determining, by a user equipment (UE), at least two carriers for uplinktransmission in a cell currently connected by the UE, and determining acarrier for uplink control information (UCI) transmission from the atleast two carriers for uplink transmission, determining, by the UE, arelative frequency-domain position and a time-domain starting positionoccupied by UCI on the determined carrier for UCI transmission, andretuning, by the UE, a center radio frequency of the UE to a centerfrequency of the carrier for UCI transmission, and transmitting the UCIaccording to the relative frequency-domain position and the time-domainstarting position occupied by the UCI, in which, the UE receives andtransmits information on one carrier at one time.

Preferably, the carrier for UCI transmission is different from a carrierused for uplink data transmission of the UE, or the carrier for UCItransmission is different from an uplink carrier corresponding to adownlink channel of the UE.

Preferably, determining, by the UE, the at least two carriers for uplinktransmission includes, determining, by the UE, the at least two carriersfor uplink transmission according to first signaling sent from a basestation, or determining, by the UE, an uplink carrier corresponding to adownlink anchor carrier or a carrier where a random access channel istransmitted as one carrier for uplink transmission, and determiningother carriers for uplink transmission according to second signalingsent from the base station or according to a predefined rule.

Preferably, determining the carrier for UCI transmission includes,determining, by the UE, the carrier for UCI transmission according tothird signaling sent from the base station; in which the third signalingis configured to indicate the carrier for UCI transmission from thecarriers for uplink transmission, or determining, by the UE, the carrierfor UCI transmission according to the first signaling or the secondsignaling.

Preferably, in a circumstance where the UE determines the uplink carriercorresponding to the downlink anchor carrier or a carrier where anarrowband random access channel (NPRACH) is transmitted as one carrierfor uplink transmission, and determines the other carriers for uplinktransmission according to the second signaling sent from the basestation or according to the predefined rule, the UE determines thecarrier for UCI transmission according to the predefined rule.

Preferably, the predefined rule is: transmitting the UCI on the othercarriers for uplink transmission, or transmitting the UCI on an uplinkcarrier corresponding to a downlink control channel of the UE.

Preferably, determining the time-domain starting position occupied bythe UCI includes, determining a first valid uplink transmission positionstarting from an end position of a downlink data channel and satisfyinga specified time offset as the time-domain starting position, in whichthe specified time offset is a preset minimum time offset, or thespecified time offset is a time offset determined according to signalingsent from the base station.

Preferably, determining the time offset according to the signaling sentfrom the base station includes, directly determining one of several timeoffsets as the time offset, where the several time offsets are absolutetime offsets, or determining one minimum time offset plus X uplink timeunits as the time offset, where X uplink time units are determinedaccording to the signaling sent from the base station.

Preferably, determining the time offset according to the signaling sentfrom the base station includes, determining one of a time offset setaccording to DCI sent from the base station as the time offset.

Preferably, when the UE determines the relative frequency-domainposition and the time-domain starting position occupied by the UCI, themethod further includes determining a time-domain length of the UCIaccording to a length of one UCI transmission and the number ofrepetitions of the UCI, in which the length of one UCI transmission isone subframe or two slots.

Preferably, the number of repetitions of the UCI is configured throughRRC.

Preferably the length of one subframe or two slots is 1 millisecond or 4milliseconds.

Preferably, determining a valid uplink transmission position includesone of the following, determining an uplink subframe determinedaccording to an uplink and downlink subframe configuration in a timedivision duplex (TDD) system as the valid uplink transmission position,determining the uplink subframe determined according to the uplink anddownlink subframe configuration in the TDD system and an uplink pilottime slot (UpPTS) in a special subcarrier as the valid uplinktransmission position, or determining the valid uplink transmissionposition according to a number of symbols contained in the UpPTS in thespecial subframe or according to a special subframe configuration; inwhich if the TDD system includes two continuous uplink subframes or aneven number of continuous uplink subframes, then the uplink subframedetermined according to the uplink and downlink subframe configurationin the current TDD system is determined as the valid uplink transmissionposition, or otherwise, the valid uplink transmission position isdetermined according to the number of symbols contained in the UpPTS inthe special subframe or according to the special subframe configuration,determining the uplink subframe and the UpPTS in the special subframe asthe valid uplink transmission position, or determining the uplinksubframe as the valid uplink transmission position according to aconfiguration configured by signaling from the base station, determiningwhether respective uplink carriers and the UpPTS in the special subframeare used as the valid uplink transmission position according to a bitmapindicator carried in the signaling from the base station.

Preferably, determining the valid uplink transmission position accordingto the number of symbols contained in the UpPTS in the special subframeincludes, if the number of symbols contained in the UpPTS is larger thana preset threshold, then determining the UpPTS and the uplink subframeas the valid uplink transmission position, or otherwise, determining theuplink subframe as the valid uplink transmission position, or if theuplink and downlink configuration in the TDD system is a specifieduplink and downlink configuration, and the number of symbols containedin the UpPTS is larger than the preset threshold, then determining theUpPTS and the uplink subframe as the valid uplink transmission position,or otherwise, determining the uplink subframe as the valid uplinktransmission position.

Preferably, determining the valid uplink transmission position accordingto the special subframe configuration comprises, if a current specialsubframe configuration is preset or is a specified special subframeconfiguration configured by the base station, then determining the UpPTSand the uplink subframe as the valid uplink transmission position, orotherwise, determining the uplink subframe as the valid uplinktransmission position, or if the uplink and downlink configuration inthe TDD system is a specified uplink and downlink configuration, and thecurrent special subframe configuration is preset or is a specifiedspecial subframe configuration configured by the base station, thendetermining the UpPTS and the uplink subframe as the valid uplinktransmission position, or otherwise, determining the uplink subframe asthe valid uplink transmission position.

A method for receiving uplink control information, including,determining, by a base station, at least two carriers for uplinktransmission allocated for a user equipment (UE) in a cell currentlyconnected by the UE, and determining a carrier for uplink controlinformation (UCI) transmission of the UE from the at least two carriersfor uplink transmission, determining, by the base station, a relativefrequency-domain position and a time-domain starting position occupiedby UCI on the determined carrier for UCI transmission, receiving, by thebase station, the UCI, on the carrier for UCI transmission of the UE,according to the relative frequency-domain position and the time-domainstarting position occupied by the UCI, in which, the UE receives andtransmits information on one carrier at one time.

Preferably, when the base station configures the carrier used by the UEto transmit the UCI, the base station configures carriers used bymultiple users to transmit UCI as a same carrier.

Preferably, when the base station determines the time-domain startingposition, the base station determines a time-domain starting positionoccupied by UCI of multiple UEs as a same position.

Preferably, when the base station determines the time-domain startingposition, the base station determines time-domain starting positionsoccupied by different UCI of the UEs as a same position.

An apparatus for transmitting uplink control information, including: acarrier determination unit, a frequency-domain and time-domaindetermination unit and a transmission unit; in which the carrierdetermination unit is configured to determine at least two carriers foruplink transmission in a cell currently connected, and determine acarrier for uplink control information (UCI) transmission from the atleast two carriers for uplink transmission, the frequency-domain andtime-domain determination unit is configured to be use by a userequipment (UE) to determine a relative frequency-domain position and atime-domain starting position occupied by UCI on the determined carrierfor UCI transmission, and the transmission unit is configured to retunea center radio frequency of the UE to a center frequency of the carrierfor UCI transmission, and transmit the UCI according to the relativefrequency-domain position and the time-domain starting position occupiedby the UCI; in which the transmission unit transmits information on onecarrier at one time.

An apparatus for receiving uplink control information, including: acarrier determination unit, a frequency-domain and time-domaindetermination unit and a receiving unit; in which the carrierdetermination unit is configured to determine at least two carriers foruplink transmission allocated for a user equipment (UE) in a cellcurrently connected by the UE, and determine a carrier for uplinkcontrol information (UCI) transmission of the UE from the at least twocarriers for uplink transmission; in which the UCI and uplink data ofthe UE are transmitted on different carriers, the frequency-domain andtime-domain determination unit is configured to determine a relativefrequency-domain position and a time-domain starting position occupiedby UCI on the determined carrier for UCI transmission, and the receivingunit is configured to receive the UCI on the carrier for UCItransmission of the UE according to the relative frequency-domainposition and the time-domain starting position occupied by the UCI; inwhich the UE transmits information on one carrier at one time.

In addition, the present disclosure provides a method and apparatus fortransmitting the center frequency of a carrier in a TDD system, whichcan provide a more flexible operation mode for the TDD system, andefficiently improve the utilization of radio frequency spectrum,especially for to a scenario where a narrowband system operates ininband or a guardband of a wide band system.

To achieve the foregoing object, the present disclosure uses thefollowing solutions, A method for transmitting signals in a timedivision duplex (TDD) narrowband system, including, obtaining, by a UE,a first carrier of the TDD narrowband system, if an uplink or downlinkcarrier determined as the first carrier locates in inband or a guardbandof a TDD wideband system, obtaining, by the UE, indication informationof a second carrier corresponding to the first carrier, determining anoffset between the first carrier and the second carrier of the TDDnarrowband system according to the indication information, andcalculating a center frequency of the second carrier corresponding tothe first carrier according to the offset and a center frequency of thefirst carrier, transmitting or receiving, by the UE, signals accordingto the calculated center frequency of the second carrier, in which whenthe first carrier is an uplink carrier, the second carrier is a downlinkcarrier, when the first carrier is a downlink carrier, the secondcarrier is an uplink carrier.

Preferably, when the first carrier is a downlink carrier, the downlinkcarrier is an anchor carrier or a non-anchor carrier.

Preferably, the indication information of the second carrier isconfigured in a system information block (SIB) or a master informationblock (MIB).

Preferably, the indication information of the second carrier includes atleast one piece of the following information: information of an offsetfrom the center frequency of the first carrier, information of physicalresource blocks occupied in the TDD wideband system, information of arelative position to the TDD wideband system, information of acell-specific reference signal (CRS) sequence.

Preferably, the UE determining that the first carrier locates in inbandor the guardband of the TDD wideband system includes: the UE determiningthat the first carrier is in inband or the guardband of the TDD widebandsystem according to one or more of the following channels orinformation: synchronization channel, master information block, systeminformation block, UE-specific radio resource control (RRC) signaling,physical layer indication information, or media access control (MAC)layer indication information.

Preferably, when the first carrier is an uplink carrier, the uplinkcarrier obtained by the UE is an uplink carrier used for transmitting arandom access channel.

Preferably, when the first carrier is a downlink carrier, and thedownlink carrier obtained by the UE locates in inband of the TDDwideband system, and cell IDs of the TDD narrowband system and cell IDsof the TDD wideband system are same, the indication information of thesecond carrier includes information of a CRS sequence.

Preferably, the UE transmitting or receiving the signals according tothe center frequency of the second carrier includes: the UE retuning acenter radio frequency to the calculated center frequency of the secondcarrier, and transmitting or receiving the signals.

A user equipment (UE) in a time-division duplex (TDD) narrowband system,including: an obtaining unit, a calculation unit and a transmissionunit; in which the obtaining unit is configured to obtain a firstcarrier of the TDD narrowband system, the calculation unit is configuredto, if an uplink or a downlink carrier determined as the first carrierlocates in inband or a guardband of a TDD wideband system, obtainindication information of a second carrier corresponding to the firstcarrier, determine an offset between the first carrier and the secondcarrier of the TDD narrowband system according to the indicationinformation, and calculate a center frequency of the second carriercorresponding to the first carrier according to the offset and thecenter frequency of the first carrier, and the transmission unit isconfigured to transmit or receive signals according to the centerfrequency of the second carrier calculated by the calculation unit, inwhich when the first carrier is an uplink carrier, the second carrier isa downlink carrier; when the first carrier is a downlink carrier, thesecond carrier is an uplink carrier.

As can be seen from the foregoing technical solutions, in the presentdisclosure, a UE determines at least two carriers for uplinktransmission in a cell currently connected by the UE, and determines acarrier for transmitting UCI from the at least two carriers for uplinktransmission; in which, the UE receives and transmits information on onecarrier at one time. On the determined carrier for transmitting the UCI,the UE determines a relative frequency-domain position and a time-domainstarting position occupied by the UCI. The UE retunes a center radiofrequency of the UE to a center frequency of the carrier fortransmitting the UCI, and transmits the UCI according to the relativefrequency-domain position and the time-domain starting position occupiedby the UCI. In this way, the UE can support at least two uplink carriersin a same cell, so as to efficiently transmit UCI.

The preferably solutions of the present disclosure also transmit UCI anduplink data on two different uplink carriers in a cell, so as toefficiently improve the uplink data rate, especially for narrowbandsystems that work in a TDD frequency band and a FDD frequency band.

The solutions of the present disclosure provides a more flexibleconfiguration for a narrowband system that works in a guardband mode oran inband mode, especially for a narrowband system where an anchorcarrier and non-anchor carriers are transmitted in inband or a guardbandof a wideband system, which improves the utilization of radio spectralresources and guarantees a UE having low complexity. The solutions ofthe present disclosure are applicable to narrowband systems that work ina TDD frequency band and a FDD frequency band, especial to a narrowbandsystem that works in a TDD frequency band.

An objective of the present disclosure is to overcome the deficienciesin the prior art and provide a method and user equipment for requestingrandom access, which are applicable to TDD communication systems and canbe deployed within an LTE band or an LTE guard band, which can also beused for standalone TDD NB-IoT system.

For this purpose, the present disclosure provides a method forrequesting random access, comprising the following steps of, determininga time division duplex (TDD) uplink time-domain resource, determining,according to the TDD uplink time-domain resource, a time-domain resourceused for transmitting a narrowband physical random access channel(NPRACH), determining a time-domain format of an NPRACH transmissiongroup, where the time-domain format comprising: one NPRACH transmissiongroup comprises a number of transmission units which are discontinuousin time domain, and one transmission unit comprises one or more NPRACHsymbol groups which are continuous in time domain, and transmitting, onthe determined time-domain resource used for transmitting NPRACH, anNPRACH transmission group in the time-domain format.

Preferably, the one transmission group comprises a number oftransmission units which are discontinuous in time domain comprises: onetransmission group comprises at least two transmission units which arediscontinuous in time domain.

Preferably, the step of determining, according to the TDD uplinktime-domain resource, a time-domain resource used for transmittingNPRACH comprises: determining a number of continuous TDD uplinktime-domain sections according to the TDD uplink time-domain resource,one continuous TDD uplink time-domain section being constituted by anyone of the following ways: by a number of continuous uplink subframes,or by one special subframe and a number of continuous uplinksubframe(s), and the step of transmitting, on the determined time-domainresource used for transmitting NPRACH, an NPRACH transmission group inthe time-domain format comprises: correspondingly transmitting, in onecontinuous TDD uplink time-domain section, one transmission unit in theNPRACH transmission group.

Preferably, the step of correspondingly transmitting, on one continuousTDD uplink time-domain section, one transmission unit in the NPRACHtransmission group comprises: correspondingly transmitting, on onecontinuous TDD uplink time-domain section, one transmission unit in theNPRACH transmission group, where the end of this transmission unit beinglocated before the end of this continuous TDD uplink time-domainsection.

Preferably, the step of correspondingly transmitting, on one continuousTDD uplink time-domain section, one transmission unit in the NPRACHtransmission group comprises: determining a timing advance (TA) used forcorrecting the time to transmit one transmission unit, andcorrespondingly transmitting; and according to the TA, transmitting onetransmission unit of the NPRACH transmission group on one continuous TDDuplink time-domain section.

Preferably, the step of determining the TA used for correcting the timeto transmit one transmission unit and correspondingly transmitting,according to the TA and on one continuous TDD uplink time-domainsection, one transmission unit in the NPRACH transmission groupcomprises:

determining the TA as Ts with m time units, and transmitting, on a UpPTSand a number of continuous uplink subframe(s) after the UpPTS, onetransmission unit in the NPRACH transmission group, and correcting thetime-domain starting transmission position for this transmission unit asthe starting position of Ts with m time units before the UpPTS.

An ending transmission position for this transmission unit in timedomain comprises: the transmission lasting until the first uplinksubframe after the UpPTS, or the transmission lasting until the last oneof all continuous uplink subframes after the UpPTS, or the transmissionlasting for the length of one NPRACH symbol group.

Preferably, the NPRACH symbol group comprises one cyclic prefix (CP) andthree to five symbols, and the total length of each symbol group is notgreater than 43008*Ts, where 30720*Ts=1 ms; or,

the NPRACH symbol group comprises one CP and three to six symbols, andthe total length of each symbol group is not greater than 14336 Ts,where 30720*Ts=1 ms.

Preferably, the step of determining TDD uplink time-domain resourcecomprises, determining valid uplink subframe(s) as TDD uplinktime-domain resource, wherein the valid uplink subframe(s) is(are)indicated by the received valid uplink subframe(s) configurationinformation; or,

determining subframe(s) other than valid downlink subframe(s) as TDDuplink time-domain resource, wherein the valid downlink subframe(s)is(are) indicated by the received valid downlink subframe configurationinformation; or,

determining uplink subframe(s) and an uplink pilot time slot (UpPTS) asTDD uplink time-domain resource, wherein the uplink subframe(s) and theUpPTS are indicated by the received uplink-downlink configurationinformation.

Preferably, after the step of determining the time-domain format for aNPRACH transmission group, the method comprises the step of: determininga frequency-domain position for transmitting an NPRACH transmission unitin a frequency-hopping transmission manner, where a frequency-domainresource for frequency-hopping transmission is determined by at leastone of following: the configured carrier position, subcarrier groupposition and subcarrier position, and a frequency-hopping pattern ispredefined or determined by a cell ID or determined by a random sequencegenerated by using a cell ID as a seed, and the step of correspondinglytransmitting, on one continuous TDD uplink time-domain section, onetransmission unit in the NPRACH transmission group comprises:transmitting, on one continuous TDD uplink time-domain section and atthe determined frequency-domain position for transmitting an NPRACHtransmission unit, one transmission unit in the NPRACH transmissiongroup.

Preferably, the time-domain format further comprises: phases between twoadjacent transmission units are continuous or the phases are fixed.

Preferably, the time-domain format further comprises: at least two thefrequency-hopping intervals between symbols groups in the NPRACHtransmission group are different.

Preferably, the step of determining a TA used for correcting the time totransmit one transmission unit comprises: determining a TA used forcorrecting the time to transmit one transmission unit, according to atleast one of the following: received radio resource control (RRC)signaling, special subframe configuration information, uplink-downlinkconfiguration information, a TA value corresponding to a preset NPRACHsymbol group time-frequency format and a predetermined fixed TA value.

Preferably, the step of correspondingly transmitting, on one continuousTDD uplink time-domain section, one transmission unit in the NPRACHtransmission group comprises: determining, according to any one of thedistribution of uplink subframe(s) and special subframe(s), the numberof uplink subframe(s) in a corresponding continuous TDD uplinktime-domain section, and the received reference point and information toindicate the offset, the starting position in time-domain of thetransmission of the first transmission unit in the NPRACH transmissiongroup, and transmitting this transmission unit in the correspondingcontinuous TDD uplink time-domain section.

Preferably, the step of correspondingly transmitting, on one continuousTDD uplink time-domain section, one transmission unit in the NPRACHtransmission group comprises, determining, according to any one of thereceived RRC signaling, the value corresponding to the preset NPRACHsymbol group time-frequency format and an uplink-downlink switchingperiod, a time interval between two continuous transmission units;determining, according to the time interval and the time-domaintransmission position of the first transmission unit in the NPRACHtransmission group, a time-domain transmission position of the secondtransmission unit or the subsequent transmission unit(s); andtransmitting the second transmission unit or the subsequent transmissionunit(s) on the corresponding continuous TDD uplink time-domain section.

Preferably, the step of transmitting, on the determined time-domainresource used for transmitting NPRACH, an NPRACH transmission group inthe time-domain format comprises: determining the repetition times N fortransmissions of the NPRACH transmission group, and repeatedlytransmitting, on the determined time-domain resource used fortransmitting NPRACH, the NPRACH transmission group with the time-domainformat for N times.

Preferably, the step of determining a time-domain format for the NPRACHtransmission group comprises: determining the time-domain format for theNPRACH transmission group according to at least one of the followingparameters: TDD uplink time-domain resource, an uplink subframeconfiguration, a special subframe configuration, an NPRACH formatconfiguration and frequency-band deployment mode.

For this purpose, the present disclosure further provides a method forpredicting a random access timing advance, comprising steps of,receiving a narrowband physical random access channel (NPRACH)transmission group, wherein one NPRACH transmission group comprises anumber of transmission units which are discontinuous in time domain, onetransmission unit comprises one or more NPRACH symbol groups which arecontinuous in time domain, and phases between two adjacent transmissionunits are continuous or the phases are fixed, determining a phasedeviation according to a time-frequency interval and/or frequency-domaininterval between a number of pairs of adjacent transmission units in theNPRACH transmission group, and/or determining a phase deviationaccording to a frequency-domain interval between different symbol groupsin the transmission unit(s), and determining a timing advance (TA)according to the phase deviation, and transmitting the TA to indicate aUE to adjust a time-domain position for transmitting an NPRACHtransmission unit.

For this purpose, the present disclosure further provides a userequipment for requesting random access, comprising, an uplink resourcedetermining module configured to determine a time division duplex (TDD)uplink time-domain resource, a transmission resource determining moduleconfigured to determine, according to the TDD uplink time-domainresource, a time-domain resource used for transmitting a narrowbandphysical random access channel (NPRACH), a transmission formatdetermining module configured to determine a time-domain format for anNPRACH transmission group, the time-domain format comprising thefollowing: one NPRACH transmission group comprises at least twotransmission units which are discontinuous in time domain, and onetransmission unit comprises one or more NPRACH symbol groups which arecontinuous in time domain, and an NPRACH transmission module configuredto transmit, on the determined time-domain resource used fortransmitting NPRACH, an NPRACH transmission group in the time-domainformat

Compared with the prior art, the present disclosure has varioustechnical effects, including but not limited to the following technicaleffects: by designing a time-domain format for NPRACH transmissionaccording to the characteristics of TDD uplink time-domain resource, arandom access process can be applied to an NB-IoT communication systembased on TDD, so that the existing NB-IoT system based on FDD can beapplicable to the operation mode of TDD. Accordingly, a higherutilization rate of spectrum resources is achieved, and the systemthroughput and connection efficiency of the NB-IoT system in a scenariowhere a large number of UEs are to be connected are significantlyimproved.

Advantageous Effects of Invention

Various embodiments of the present disclosure provide a uplink controlinformation transmission scheme and a random access scheme that are moreeffective.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a radio communication system;

FIG. 2 illustrates a base station in the wireless communication systemaccording to various embodiments of the present disclosure;

FIG. 3 illustrates a user equipment (UE) in the wireless communicationsystem according to various embodiments of the present disclosure;

FIG. 4 is a schematic diagram of a basic flow of a method fortransmitting uplink control information (UCI) according to the presentdisclosure;

FIG. 5 is a first schematic diagram of UCI transmission in a timedivision duplex (TDD) system;

FIG. 6 is a second schematic diagram of UCI transmission in the TDDsystem;

FIG. 7 is a third schematic diagram of UCI transmission in the TDDsystem;

FIG. 8 is a schematic diagram of a method for indicating afrequency-domain position for transmitting UCI;

FIG. 9 is a schematic diagram of a detailed flow of a method fortransmitting UCI according to an embodiment of the present disclosure;

FIG. 10 is a schematic diagram of a basic flow of a method for receivingUCI according to the present disclosure;

FIG. 11 is a schematic diagram illustrating a base station schedules UCIof multiple UEs;

FIG. 12 is a schematic diagram illustrating a base station schedulesmultiple downlink transmissions for one UE;

FIG. 13 is a schematic diagram for transmitting UCI in a scenario wherethere is a collision between UCI and physical uplink shared channel(PUSCH);

FIG. 14 is a schematic diagram of a basic structure of an apparatus fortransmitting UCI according to the present disclosure;

FIG. 15 is a schematic diagram of a basic structure of an apparatus forreceiving UCI according to the present disclosure;

FIG. 16 is a basic flowchart of signal transmission in the TDD systemguardband operation mode or the inband operation mode according to thepresent disclosure;

FIG. 17 is a schematic diagram of uplink and downlink carriers in a TDDnarrowband system;

FIG. 18 is an exemplary flowchart of a UE obtaining the center frequencyof an uplink carrier;

FIG. 19 is a flowchart of a method for requesting random accessaccording to the present disclosure;

FIG. 20 is a flowchart of a method for predicting a random access timingadvance (TA) according to the present disclosure;

FIG. 21 is a schematic diagram of an narrowband physical random accesschannel (NPRACH) transmission group according to the present disclosure;

FIG. 22 is a schematic diagram of a first type of NPRACH transmissionaccording to the present disclosure;

FIG. 23 is a schematic diagram of a second type of NPRACH transmissionaccording to the present disclosure;

FIG. 24 is a schematic diagram of a third type of NPRACH transmissionaccording to the present disclosure; and

FIG. 25 is a module diagram of a UE according to the present disclosure.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present disclosure will be described in detailhereinafter. The examples of these embodiments have been illustrated inthe accompanying drawings throughout which same or similar referencenumerals refer to same or similar elements or elements having same orsimilar functions. The embodiments described with reference to theaccompanying drawings are illustrative, merely used for explaining thepresent disclosure and should not be regarded as any limitationsthereto.

It should be understood by a person of ordinary skill in the art thatsingular forms “a”, “an”, “the”, and “said” can be intended to includeplural forms as well, unless otherwise stated. It should be furtherunderstood that terms “comprise/comprising” used in this specificationspecify the presence of the stated features, integers, steps,operations, elements and/or components, but not exclusive of thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or combinations thereof. It shouldbe understood that, when a component is referred to as being “connectedto” or “coupled to” another component, it can be directly connected orcoupled to other elements or provided with intervening elementstherebetween. In addition, “connected to” or “coupled to” as used hereincan comprise radio connection or coupling. As used herein, the term“and/or” comprises all or any of one or more associated listed items orcombinations thereof.

It should be understood by a person of ordinary skill in the art that,unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by aperson of ordinary skill in the art to which the present disclosurebelongs. It should be further understood that terms, such as thosedefined in commonly used dictionaries, should be interpreted as having ameaning that is consistent with their meanings in the context of theprior art and will not be interpreted in an idealized or overly formalsense unless expressly so defined herein.

It should be understood by a person of ordinary skill in the art thatthe term “terminal” and “terminal equipment” as used herein compassesnot only devices with a radio signal receiver having no emissioncapability but also devices with receiving and emitting hardware capableof carrying out bidirectional communication over a bidirectionalcommunication link. Such devices can comprise cellular or othercommunication devices with a single-line display or multi-line displayor without a multi-line display; personal communication systems (PCSs)with combined functionalities of speech, data processing, facsimileand/or data communication; personal digital assistants (PDAs), which mayinclude RF receivers, pagers, internet networks/intranet accesses, webbrowsers, notepads, calendars and/or global positioning system (GPS)receivers; and/or conventional laptop and/or palmtop computers or otherdevices having and/or including a RF receiver. The “terminal” and“terminal equipment” as used herein can be portable, transportable,mountable in transportations (air, sea and/or land transportations), orsuitable and/or configured to run locally and/or distributed in otherplaces in the earth and/or space for running. The “terminal” or“terminal equipment” as used herein can be a communication terminal, aninternet terminal, a music/video player terminal. For example, it can bea PDA, a mobile internet device (MID) and/or a mobile phone with amusic/video playback function, or can be equipment such as a smart TVand a set-top box.

In a long term evolution (LTE) system, uplink control information (UCI)is transmitted on the two ends of the system bandwidth. In this way, theLTE system not only can obtain a frequency hopping (FH) gain to providedecoding performance, but also can efficiently avoid fragmentation ofuplink resources, so as to provide resources that can be continuouslyallocated for a physical uplink shared channel (PUSCH). In an enhancedmachine type communication (eMTC) system, the LTE system bandwidth isdivided into several narrow bands, in which each narrow band consists of6 physical resource blocks (PRBs) used for PUSCH transmission. In theLTE system bandwidth, a physical uplink control channel (PUCCH) thatcarries UCI indicates a PRB position using a radio resource control(RRC) indicator, and further determines the frequency-domain resourceposition of the UCI according to the position of an MTC physicaldownlink control channel (MPDCCH) and the indicator in the DCI. 3rdgeneration partnership project (3GPP) Rel-13 defines a narrowbandInternet of things (NB-IoT) system the bandwidth of which is only 200kHZ, i.e., one PRB, and UCI of it is transmitted using the narrowbandphysical uplink shared channel (NPUSCH) format 2, and the time-frequencyphysical resources of the NPUSCH format 2 is indicated by DCI, and thecandidate time-frequency positions of it are predefined in the standard.

In 3GPP Rel-15, an NB-IoT system that works in a time division duplex(TDD) frequency band will be standardized, and since the number ofuplink slots is limited, if the NPUSCH format 2 and the rule of the FDDNB-IoT continue to be used, then uplink resource granularity will beseriously destroyed, thus seriously affecting the actual uplink datarate of the system. Therefore, it is yet a problem to be solvedregarding how to effectively transmit UCI, especially for a narrowbandsystem that works in the TDD frequency band, e.g., a TDD NB-IoT system.

In addition, since the NB-IoT system bandwidth is only 200 kHz, uplinksubframes on the anchor carrier will be used by a downlink commonchannel (e.g., narrowband primary synchronization signal (NPSS),narrowband secondary synchronization signal (NSSS), and narrowbandphysical broadcast channel (NPBCH)), which will cause uplink anddownlink proportions are not even. Therefore, a more flexiblemulti-carrier operation mode needs to be defined in the TDD NB-IoTsystem to balance the utilization of the uplink and downlink resources.

For a TDD NB-IoT system that operates in inband or a guardband of theLTE system, to keep the orthogonality with the LTE system and strictlyalign with PRB resources in the LTE system, there should be a certainoffset between the uplink and downlink center frequencies of the TDDNB-IoT system. In addition, since the radio frequency precision of abase station in the NB-IoT system cannot be achieved by a UE in theNB-IoT system, to meet the requirement of LTE outband leakage, for theguardband operation mode, the NB-IoT UE cannot perform uplinktransmission over some carrier frequencies in some guardbands. That isto say, there is no uplink carrier corresponding to the downlinkcarriers of some TDD NB-IoT systems, and therefore, the base stationneeds to additionally configure an uplink carrier corresponding to thesedownlink carriers.

The present disclosure accordingly provides a solution to solve theabove problems of carrier configuration.

In addition, in 3GPP Rel-13, for a standard NB-IoT system, thefrequency-band distribution can be an LTE in-band deployment, an LTEguard-band deployment or a stand-alone deployment. In Rel-14,positioning, broadcast, multi-carrier or other enhancement technologiesare incorporated into the 3GPP. At present, FDD systems have beenincorporated into standard NB-IoT systems, and the NB-IoT terminals areHD-FDD terminals. To better serve different applications in the internetof things (IoT) and to meet different requirements, the normalization ofan NB-IoT system in the TDD frequency spectrum will be developed in 3GPPRel-15.

A random access process is an important way to establish a connectionbetween a network side and a terminal side in a mobile communicationsystem, and the performance of the random access directly influences theworking efficiency of the system. In an NB-IoT system based on FDD, inthe frequency domain, an NPRACH (random access channel) is in a form ofa single-carrier having a subcarrier spacing of 3.75 kHz; while in thetime domain, the NPRACH is a symbol group consisting of one cyclicprefix (CP) and five symbols, wherein every four symbols form one NPRACHtransmission. However, since the symbol length corresponding to 3.75 kHzis 266.67 us and a TDD system has a frame structure totally differentfrom an FDD system, the NPRACH transmission needs to be kept consistentwith the uplink-downlink configuration of the TDD LTE when the NB-IoTsystem based on FDD is deployed within an LTE band or an LTE guard band.Therefore, existing NPRACH for FDD are not applicable to TDD systems interms of format, size, transmission position or more.

In view of this, it is necessary to provide a method and user equipmentfor requesting random access which can solve the problems describedabove.

FIG. 1 illustrates an exemplary radio communication system 100 accordingto embodiments of the present disclosure, in which, a UE detectsindication information. The radio communication system 100 includes oneor more fixed infrastructure units to form a network distributed in ageographical area. The infrastructure unit may be called as access point(AP), access terminal (AT), base station (BS), node B (Node-B), evolvedNodeB (eNB), next generation NodeB (gNB), or other terminologies used inthe technical field. As shown in FIG. 1, one or more infrastructureunits 101 and 102 provide services for several mobile stations (MSs), oruser equipments (UEs), or terminal devices, or users 103 and 104 in theserving area which for example is a cell or a cell sector. In somesystems, one or more BSs may be communicatively coupled to a controllerthat forms an access network, and the controller may be communicativelycoupled to one or more core networks. The present disclosure does notlimit the radio communication system to a specific type.

In the time domain and/or the frequency domain, the infrastructure units101 and 102 respectively transmit downlink (DL) communication signals112 and 113 to the UEs 103 and 104. The UEs 103 and 104 respectivelycommunicate with the one or more infrastructure units 101 and 102through uplink (UL) communication signals 111 and 114. In an embodiment,the mobile communication system 100 is an orthogonal frequency divisionmultiplexing (OFDM)/orthogonal frequency division multiple access(OFDMA) system that includes multiple base stations and multiple UEs.The multiple base stations include the base station 101 and the basestation 102, and the multiple UEs include the UE 103 and the UE 104. Thebase station 101 communicates with the UE 103 through the uplinkcommunication signal 111 and the downlink communication signal 112. Whenthe base station has downlink packets to be transmitted to UEs, each UEwill obtain one downlink position (resource), e.g., a set of radioresources in the physical downlink shared channel (PDSCH) or narrowbanddownlink shared channel (NPDSCH). When a UE needs to transmit packets tothe base station through an uplink, the UE obtains a grant from the basestation, in which the grant allocates a physical uplink shared channel(PUSCH) or a narrowband physical uplink shared channel (NPUSH)containing a set of uplink radio resources. The UE obtains downlink oruplink scheduling information from PDCCH, or MPDCCH, or EPDCCH, orNPDCCH specific to the UE. In the following description, these channelsare unified as PDSCH, PDCCH, and PUSCH. The downlink or uplinkscheduling information and other control information carried in thedownlink control channel is referred to as downlink control information(DCI). FIG. 1 also shows different physical channels of the downlink 112and the uplink 111. The downlink 112 includes a PDCCH or EPDCCH orNPDCCH or MPDCCH 121, a PDSCH or NPDSCH 122, a physical controlformation indicator channel (PCFICH) 123, a physical multicast channel(PMCH) 124, a physical broadcast channel (PBCH) or NPBCH 125, a physicalhybrid automatic repeat request indicator channel (PHICH) 126 and aprimary synchronization signal (PSS), secondary synchronization signal(SSS), or NPSS/NSSS 127. The downlink control channel 121 sends adownlink control signal to the UE. The DCI 120 is carried on thedownlink control channel 121. The PDSCH 122 transmits data informationto the UE. The PCFICH 123 is used to transmit PDCCH decodinginformation, e.g., dynamically indicating the number of symbols used bythe PDCCH 121. The PMCH 124 carries broadcast and multicast information.The PBCH or NPBCH 125 carries a master information block (MIB), used forUE early detection and cell-wide coverage. The PHICH carries hybridautomatic repeat request (HARQ) information, and the HARQ informationindicates whether the base station correctly receives a transmittedsignal. The uplink 111 includes a physical uplink control channel(PUCCH) 131 that carries uplink control information (UCI) 130, a PUSCH132 that carries uplink data information, and a physical random accesschannel (PRACH) 133 that carries random access information. In theNB-IoT system, there is no definition for NPUCCH, and the NPUSCH format2 is used to transmit the UCI 130.

In an embodiment, the radio communication network 100 uses an OFDMA ormulti-carrier architecture, including adaptive modulation and coding(AMC) on the downlink and a next generation single-carrier FDMAarchitecture or a multi-carrier OFDMA structure used for uplinktransmission. The FDMA-based single-carrier structure includesinterleaved FDMA (IFDMA), localized FDMA (LFDMA), IFDMA, or DFT-spreadOFDM (DFT-S-OFDM) of the IFDMA. In addition, the FDMA-basedsingle-carrier architecture also includes various enhancednon-orthogonal multi-access architectures (NOMA) of the OFDMA system,e.g., PDMA (Pattern division multiple access) (PDMA), SCMA (Sparse codemultiple access (SCMA), MUSA (Multi-user shared access (MUSA), LCRS FDS(Low code rate spreading Frequency domain spreading (LCRS FDS), NCMA(Non-orthogonal coded multiple access (NCMA), RSMA (Resource spreadingmultiple access (RSMA), IGMA (Interleave-grid multiple access (IGMA),Low density spreading with signature vector extension (LDS-SVE), Lowcode rate and signature based shared access (LSSA), Non-orthogonal codedaccess (NOCA), Interleave division multiple access (IDMA), Repetitiondivision multiple access (RDMA), Group orthogonal coded access (GOCA),Welch-bound equality based spread MA (WSMA), and so on.

In an OFDMA system, usually downlink or uplink radio resources thatcontain a set of subcarriers on one or more OFDM symbols are allocatedto serve the remote elements. An exemplary OFDMA protocol includesevolved LTE and IEEE 1003.16 standards developed from the 3GPP UMTSstandard. The architecture may also include transmission techniques,e.g., multi-carrier CDMA (MC-CDMA), multi-carrier direct sequence CDMA(MC-DS-CDMA), and orthogonal frequency and code division multiplexing(OFCDM) for one divisional or two divisional transmission. Or, the OFDMAsystem may be based on a simpler time-division and/or frequency-divisionmultiplexing/multiple access techniques, or combinations of thesetechniques. In an alternative embodiment, the communication system mayuse other cellular communication protocols, including but not limited toTDMA or direct sequence CDMA.

In an FDD NB-IoT system, UCI is transmitted using the NPUSCH format 2.For an uplink subcarrier gap of 3.75 kHZ, one UCI transmission onlyoccupies one subcarrier and 8 ms; and for an uplink subcarrier gap of 15kHz, one UCI transmission only occupies one subcarrier and 2 ms. For theNPUSCH format 2, a carrier actually occupied by it is indicated from apredefined table using DCI that schedules a downlink NPDSCH. To leaveenough time for a UE with low complexity to decode the NPDSCH, thefeedback time of HARQ-ACK of it is at least 12 ms. It is difficult for atraditional downlink NPDSCH feedback mechanism used for the FDD NB-IoT,to transmit uplink data at a high rate (e.g., occupying 12 subcarriers).

FIG. 2 illustrates a base station in the wireless communication systemaccording to various embodiments of the present disclosure. A structureexemplified at FIG. 2 may be understood as a structure of the basestation 101 or 102. The term “-module”, “-unit” or “-er” usedhereinafter may refer to the unit for processing at least one functionor operation and may be implemented in hardware, software, or acombination of hardware and software.

Referring to FIG. 2, the BS may include a wireless communicationinterface 210, a backhaul communication interface 220, a storage unit230, and a controller 240.

The wireless communication interface 210 performs functions fortransmitting and receiving signals through a wireless channel. Forexample, the wireless communication interface 210 may perform a functionof conversion between a baseband signal and bitstreams according to aphysical layer standard of the system. For example, in datatransmission, the wireless communication interface 210 generates complexsymbols by encoding and modulating transmission bitstreams. Further, indata reception, the wireless communication interface 210 reconstructsreception bitstreams by demodulating and decoding the baseband signal.

In addition, the wireless communication interface 210 up-converts thebaseband signal into a radio frequency (RF) band signal, transmits theconverted signal through an antenna, and then down-converts the RF bandsignal received through the antenna into the baseband signal. To thisend, the wireless communication interface 210 may include a transmissionfilter, a reception filter, an amplifier, a mixer, an oscillator, adigital-to-analog convertor (DAC), an analog-to-digital convertor (ADC),and the like. Further, the wireless communication interface 210 mayinclude a plurality of transmission/reception paths. In addition, thewireless communication interface 210 may include at least one antennaarray consisting of a plurality of antenna elements.

On the hardware side, the wireless communication interface 210 mayinclude a digital unit and an analog unit, and the analog unit mayinclude a plurality of sub-units according to operation power, operationfrequency, and the like. The digital unit may be implemented as at leastone processor (e.g., a digital signal processor (DSP)).

The wireless communication interface 210 transmits and receives thesignal as described above. Accordingly, the wireless communicationinterface 210 may be referred to as a “wireless communication unit”, a“wireless communication module”, a “transmitter” a “receiver,” or a“transceiver.” Further, in the following description, transmission andreception performed through the wireless channel may be used to have ameaning including the processing performed by the wireless communicationinterface 210 as described above.

The backhaul communication interface 220 provides an interface forperforming communication with other nodes within the network. That is,the backhaul communication interface 220 converts bitstreams transmittedto another node, for example, another access node, another BS, a highernode, or a core network, from the BS into a physical signal and convertsthe physical signal received from the other node into the bitstreams.The backhaul communication interface 220 may be referred to as a“backhaul communication unit” or a “backhaul communication module”.

The storage unit 230 stores a basic program, an application, and datasuch as setting information for the operation of the BS. The storageunit 230 may include a volatile memory, a non-volatile memory, or acombination of volatile memory and non-volatile memory. Further, thestorage unit 230 provides stored data in response to a request from thecontroller 240.

The controller 240 controls the general operation of the BS. Forexample, the controller 240 transmits and receives a signal through thewireless communication interface 210 or the backhaul communicationinterface 220. Further, the controller 240 records data in the storageunit 230 and reads the recorded data. The controller 240 may performsfunctions of a protocol stack that is required from a communicationstandard. According to another implementation, the protocol stack may beincluded in the wireless communication interface 210. To this end, thecontroller 240 may include at least one processor. According toexemplary embodiments of the present disclosure, the controller 240 maycontrol the base station to perform operations according to theexemplary embodiments of the present disclosure.

FIG. 3 illustrates a UE in the wireless communication system accordingto various embodiments of the present disclosure. A structureexemplified at FIG. 3 may be understood as a structure of the UE 103 or104. The term “-module”, “-unit” or “-er” used hereinafter may refer tothe unit for processing at least one function or operation, and may beimplemented in hardware, software, or a combination of hardware andsoftware.

Referring to FIG. 3, the UE includes a communication interface 310, astorage unit 320, and a controller 330.

The communication interface 310 performs functions fortransmitting/receiving a signal through a wireless channel. For example,the communication interface 310 performs a function of conversionbetween a baseband signal and bitstreams according to the physical layerstandard of the system. For example, in data transmission, thecommunication interface 310 generates complex symbols by encoding andmodulating transmission bitstreams. Also, in data reception, thecommunication interface 310 reconstructs reception bitstreams bydemodulating and decoding the baseband signal. In addition, thecommunication interface 310 up-converts the baseband signal into an RFband signal, transmits the converted signal through an antenna, and thendown-converts the RF band signal received through the antenna into thebaseband signal. For example, the communication interface 310 mayinclude a transmission filter, a reception filter, an amplifier, amixer, an oscillator, a DAC, and an ADC.

Further, the communication interface 310 may include a plurality oftransmission/reception paths. In addition, the communication interface310 may include at least one antenna array consisting of a plurality ofantenna elements. In the hardware side, the wireless communicationinterface 210 may include a digital circuit and an analog circuit (forexample, a radio frequency integrated circuit (RFIC)). The digitalcircuit and the analog circuit may be implemented as one package. Thedigital circuit may be implemented as at least one processor (e.g., aDSP). The communication interface 310 may include a plurality of RFchains. The communication interface 310 may perform beamforming.

The communication interface 310 transmits and receives the signal asdescribed above. Accordingly, the communication interface 310 may bereferred to as a “communication unit”, a “communication module”, a“transmitter,” a “receiver,” or a “transceiver.” Further, in thefollowing description, transmission and reception performed through thewireless channel is used to have a meaning including the processingperformed by the communication interface 310 as described above.

The storage unit 320 stores a basic program, an application, and datasuch as setting information for the operation of the UE. The storageunit 320 may include a volatile memory, a non-volatile memory, or acombination of volatile memory and non-volatile memory. Further, thestorage unit 320 provides stored data in response to a request from thecontroller 330.

The controller 330 controls the general operation of the UE. Forexample, the controller 330 transmits and receives a signal through thecommunication interface 310. Further, the controller 330 records data inthe storage unit 320 and reads the recorded data. The controller 330 mayperforms functions of a protocol stack that is required from acommunication standard. According to another implementation, theprotocol stack may be included in the communication interface 310. Tothis end, the controller 330 may include at least one processor ormicroprocessor, or may play the part of the processor. Further, the partof the communication interface 310 or the controller 330 may be referredto as a communication processor (CP). According to exemplary embodimentsof the present disclosure, the controller 330 ma control the UE toperform operations according to the exemplary embodiments of the presentdisclosure.

FIG. 4 is a flowchart of a method for transmitting uplink controlinformation according to the present disclosure.

Referring FIG. 4, in step 401, a UE determines at least two carriers foruplink transmission in a cell currently connected by the UE, anddetermines a carries for UCI transmission from the at least two carriersdetermined.

In the method of the present disclosure, the cell connected by the UEincludes at least two carriers for the UE to perform uplinktransmission. The present disclosure is especially applicable to anarrowband system, and in the narrowband system, the UE only receivesand transmits information on one carrier at one time. Preferably, UCIand uplink data of the UE may be transmitted on different carriers, orin other words, a carrier for the UE to transmit UCI and an uplinkcarrier corresponding to downlink data are different.

In step 403, the UE determines a relative frequency-domain position anda time-domain starting position occupied by UCI on the determinedcarrier for UCI transmission in step 401.

In step 405, the UE retunes its center radio frequency to a centerfrequency of the carrier for UCI transmission, and transmits the UCIaccording to the relative frequency-domain position and the time-domainstarting position occupied by the UCI.

For a UE in the NB-IoT system, it only supports UE working on onecarrier at one time, and does not support working on two carriers at thesame time. Meanwhile, as described in the foregoing, the downlink datachannel and the UCI of the UE are transmitted on different carriers, andtherefore, before the UE transmits the UCI, the UE needs to retune itscenter radio frequency to the center point of the carrier for UCItransmission, and then transmits the UCI.

Till then, the overall flow of the UCI transmission method according tothe present disclosure ends. In the following, each processing step inthe flow of the UCI transmission method will be described in detail.

Firstly, the UCI may be transmitted on an uplink control channel (e.g.,a PUCCH) or an uplink shared channel format 2 channel (e.g., an NPUSCHformat 2 channel). A carrier where the UCI is located is determined bystep 401. The UCI includes at least one piece of the followinginformation: HARQ-ACK information indicating the decoding state of adownlink data channel (i.e., a downlink shared channel), uplinkscheduling request (SR) information and periodic and/or aperiodicchannel state information (CSI).

For step 401, when determining the at least two carriers for uplinktransmission of the UE, the following several detailed approaches may beused:

Approach 1: the UE may determine respective carriers used for uplinktransmission of the UE according to signaling (e.g., RRC signaling,including: system information (SIB), UE-specific signaling, etc.) sentfrom the base station. For example, the UE may obtain the centerfrequencies of the respective carriers used for uplink transmissionaccording to the signaling, and then determine the correspondingcarriers;

Approach 2: the UE may use a carrier where an uplink carriercorresponding to the anchor carrier (a carrier where a downlinksynchronization channel is transmitted) or a carrier where a randomaccess channel (e.g., an NPRACH) is transmitted as one carrier used foruplink transmission, and then determines other carriers used for uplinktransmission according to signaling sent from the base station, oraccording to a predefined rule. The predefined rule may be defined asdemands. For example it may be defined that several carriers neighboringthe uplink carrier corresponding to the anchor carrier or adjacent thecarrier where the random access channel is transmitted are the othercarriers. For the TDD system, a downlink carrier and a correspondinguplink carrier have a same center frequency, and it is unnecessary touse additional singling to indicate them; that is to say, for the TDDsystem, a downlink carrier position determined by the UE through cellsearching is the uplink carrier position, and a carrier that transmits asynchronization channel is the anchor carrier. For the FDD system, afterthe UE determines the position of a downlink carrier, the base stationconfigures an uplink carrier corresponding to the downlink carrierthrough RRC signaling. That is to say, the uplink carrier correspondingto the anchor carrier is indicated by the RRC signaling.

For step 401, when determining the carrier for UCI transmission, thefollowing methods may be used:

Approach a: the UE determines the carrier for UCI transmission accordingto specified signaling sent from the base station. The specifiedsignaling may be the signaling that indicates the at least two carriersfor uplink transmission for the UE in the Approach 1, and that is tosay, when the base station configures the at least two carriers foruplink transmission of the UE through the signaling, the base stationdirectly indicates the carrier for UCI transmission in the signaling; orthe specified signaling may be the signaling that indicates the othercarriers for uplink transmission in the Approach 2, and that is to say,when the base station configures the other carriers for uplinktransmission through the signaling, the base station directly indicatesthe carriers for UCI transmission in the signaling. For example,preferably, the UE determines the carrier for UCI transmission accordingto RRC signaling, or physical layer information, or MAC layer signaling.Specifically, the base station respectively allocates different carriersfor UCI transmission and the uplink data of the UE through the RRCsignaling, and in this way, when the UE receives the RRC signaling, itnot only can determine the carriers used for uplink transmission, butalso can determine the carrier where the UCI is transmitted.

Approach b: after the UE determines the carriers for uplinktransmission, it determines the carrier for UCI transmission accordingto signaling additionally transmitted from the base station. That is tosay, the base station configures multiple uplink carriers for the UEaccording to the Approach 1 or the Approach 2, and then the UEdetermines which carrier should be used to transmit the UCI from themultiple uplink carriers determined according to the Approach 1 or theApproach 2, according to configuration configured by signaling such asDCI or MAC signaling, or UE-specific RRC retransmitted by the basestation.

Approach c: when using the Approach 2 to determine the carriers foruplink transmission of the UE, the carrier for UCI transmission may bedetermined according to a predefined rule. For example, a rule ispredefined as that the UCI is transmitted on another carrier other thanthe uplink carrier corresponding to a non-anchor carrier, or a carrierwhere the NPRACH is located, or the UCI is transmitted on an uplinkcarrier corresponding to the PDCCH or PDSCH, or the UCI is nottransmitted on the uplink carrier corresponding to the PDCCH or PDSCH.

FIG. 5 is a schematic diagram of UCI transmission in a TDD system. Whendetermining the carriers, the UE may obtain two carriers, e.g., acarrier 1 and a carrier 2, that can be used for uplink transmissionthrough higher layer signaling (e.g., SIB or UE-specific RRC signaling).Or the UE may perform cell searching, and obtain the position of adownlink anchor carrier, and after the UE determines that the currentsystem is a TDD system, the UE directly determines that the downlinkanchor carrier is an uplink carrier (e.g., the carrier 1 in FIG. 3), andthen the UE obtains the positions of other carriers (e.g., the carrier 2in FIG. 3) according to higher layer signaling or according to apredefined rule, and the UCI is transmitted on the other carriers (e.g.,the carrier 2 in FIG. 3). Assuming that the downlink control channelPDCCH and the downlink data channel PDSCH that is scheduled by the PDCCHare all transmitted on the carrier 1, then the UCI used for PDSCHfeedback is transmitted on the carrier 2. The UE decodes the downlinkdata channel, and generates the UCI according to a result of decodingthe downlink data channel.

In FIG. 3, a relative frequency-domain position and a time-domainstarting position for the UCI transmission may be determined using atraditional method. For example, a time offset relative to the endposition of the PDSCH and/or a frequency-domain position may beindicated by the DCI. To be specific, a time offset and/or afrequency-domain position set may be configured by RRC or may bepredefined, and the DCI indicates one value from the set. Or thesmallest time offset is predefined, e.g., 12 ms or 6 ms, and thetime-domain starting position of the UCI is a position that starts fromthe end position of the PDSCH and satisfies the smallest time offset.Further, the PUSCH used for uplink data transmission may also betransmitted on the carrier 1, which is different from the carrier usedfor UCI transmission. It should be noted that, for the TDD system, ifthe UCI and the PDSCH/PUSCH are on different carriers, then it should beensured that when performing retuning, enough time should be reservedfor the UE, i.e., reserving time, e.g., 1 ms, for retuning the centerfrequency in step 405.

In the following, the method for determining the time-domain startingposition occupied by the UCI in step 403 will be described in detail. Asshown in FIG. 3, the method for determining the time-domain startingposition may use a traditional method. However, in the TDD system, asthe uplink and downlink subframe configurations are different, the timepositions available for uplink transmission are not definite, andtherefore, if the traditional method for determining the time-domainstarting position is used, a time-domain starting position determinedmay belong to a downlink transmission time. Therefore, in the TDD systemprovided by the present disclosure, when determining the time-domainstarting position occupied by the UCI, the first valid uplinktransmission position that starts from the end position of the downlinkdata channel and satisfies the specified time offset is determined asthe time-domain starting position. The specified time offset may be apreset smallest time offset, or the specified time offset may be a timeoffset determined according to signaling sent (e.g., through RRC or MACor DCI) from the base station. In an NB-IoT FDD system, the time offsetis an absolute value, e.g., {13, 15, 17, 18}ms. However, in a TDDsystem, since different uplink and downlink configurations may causevalid uplink subframes to be noncontinuous. To better use thecharacteristics of the TDD system, and meanwhile to ensure the time fordecoding PDSCH, the time offset of UCI may be defined as the xth uplinktime unit that satisfies the smallest time offset of 12 ms, e.g., X maybe one value out of the set {0,1,2,4}, or may be indicated by downlinkDCI. One time unit may be a slot, a subframe, a symbol, the transmissionlength of one resource unit (RU), or may be an absolute time, e.g., 1ms. The set may be preset in the protocol, or may be configured throughRRC. One valid uplink position may be the time length of one UCItransmission, e.g., one subframe or one slot or two slots. For example,for a subcarrier gap of 15 kHz, the time length of one UCI transmissionis 1 ms, and for a subcarrier gap of 3.75 kHz, the time length of oneUCI transmission is 4 ms. To be specific, one UCI transmission mayconsist of 8 symbols that carry UCI data and 7 demodulation referencesignals (DMRS) used for UCI detection. For example, the first, second,sixth and seventh symbols in a slot are symbols that carry UCI data, andthe third, fourth and fifth symbols are symbols that carry DMRS, or thefirst, second and third symbols are symbols that carry DMRS and thefourth, fifth, sixth and seventh symbols are symbols that carry UCIdata. One UCI transmission spans two slots, and the UE may repeatlytransmit the UCI for several times according to configuration configuredby the base station.

In the foregoing method for determining the time-domain startingposition of the TDD system, what is different from the traditionalmethod is the first valid uplink transmission position that satisfiesthe specified time offset. Therefore, in the following, the valid uplinktransmission position will be described in detail.

FIG. 6 is a schematic diagram of UCI transmission in the TDD system,where D represents a downlink subframe determined according to a currentTDD uplink and downlink subframe configuration, and the downlinksubframe is reserved for downlink transmission; U represents an uplinksubframe determined according to the current TDD uplink and downlinksubframe configuration, and the uplink subframe is reserved for uplinktransmission; S represents a special subframe. As shown in FIG. 4, thevalid uplink transmission position is an uplink subframe determinedaccording to the current TDD uplink and downlink subframe configuration.That is to say, the UE determines the time-domain starting position ofthe resources occupied by the UCI according to the end position of thedownlink data channel transmission and the uplink subframe determinedaccording to and the uplink and downlink subframe configuration. To bespecific, the UE determines the uplink subframe position according tothe uplink and downlink subframe, and starts to transmit UCI in anuplink subframe that meets the specified time offset.

As shown in FIG. 6, assuming that the smallest time offset between PDSCHand UCI is 4 time units, then the first uplink subframe that can be usedfor UCI transmission and can satisfy the smallest 4 time units is after6 time units after the PDSCH ends. One time unit may be one slot, onesubframe, one symbol, the transmission length of one resource unit (RU),or may be an absolute value, e.g., 1 ms. In another example, DCIindicates 4 uplink time units, and then a time offset between PDSCH andUCI is the smallest time offset plus 4 uplink time units. To bespecific, for example, the smallest time offset is 12 ms, and then theuplink subframe for UCI transmission is the fourth uplink time unitafter 12 ms after the PDSCH. Since uplink time units may benoncontinuous, then the absolute time may be larger than 12 ms+4 ms(assuming that one uplink time unit is 1 ms).

FIG. 7 is another schematic diagram of UCI transmission in the TDDsystem, in which an uplink pilot slot (UpPTS) in a special subframe maybe used as a valid uplink transmission position, and the valid uplinktransmission position may be determined according to the followingapproaches:

Approach 1, an uplink subframe U determined according to a currentuplink and downlink subframe configuration and an UpPTS in a specialsubframe both can be used as the valid uplink transmission position. Tobe specific, the UE determines the uplink subframe position according tothe uplink and downlink subframe configuration, and starts to transmitUCI in the first uplink subframe that satisfies the smallest time offsetor in the UpPTS in the special subframe. For example, the smallest timeoffset between PDSCH and UCI is 4 time units, and the first uplinksubframe or an UpPTS in a special subframe that can be used for UCItransmission after the smallest time units after the PDSCH is an UpPTSafter 5 time units after the PDSCH, and in this case, uplink controlinformation 1 is transmitted once (and retransmitted once) in the UpPTSand a following uplink indicator.

In addition, since the number of symbols in the UpPTS is configuredaccording to special subframe configuration information, and in someconfigurations for the LTE special subframe, there is only one symbol inthe UpPTS, used for the sounding reference signal (SRS) transmission, orthere are only 2 or 3 symbols. In this case, it is not good for UCIcoding, and meanwhile it may cause problems for the base station tosemi-statically configure the number of repetitions of UCI. Therefore,in the Approach 2, a threshold may be preset, and when the number ofsymbols contained in the special subframe is larger than the presetthreshold (e.g., there are 5 or 6 symbols in the UpPTS), the UpPTS inthe special subframe and uplink subframes can be used as valid uplinktransmission positions, and when the number of symbols contained in thespecial subframe is not larger than the preset threshold, only uplinksubframes can be used as valid uplink transmission positions. To bespecific, it may be defined that no matter how many symbols in theUpPTS, the UpPTS will not be used for uplink transmission.

Or in Approach 3, whether the UpPTS in the special subframe can be usedas the uplink transmission position is determined according to a specialsubframe configuration currently used. Preferably, it may be preset ormay be configured by the base station that UpPTS corresponding to whichspecial subframe configurations can be used as the valid uplinktransmission position. For example, in a detailed standard, it maydefine that, under some special subframe configurations (e.g., thespecial subframe configurations 5˜9), UpPTS can be used as the validuplink transmission position, and can be used for UCI transmission, andunder some other special subframe configurations (e.g., the specialsubframe configurations 0˜4), UpPTS cannot be used as the valid uplinktransmission position, and cannot be used for UCI transmission.

Or, in Approach 4, a valid uplink transmission position may bedetermined based on a preset threshold (or a specific special subframeconfiguration) in combination with a specific uplink and downlinkconfiguration. To be specific, under the specific uplink and downlinkconfiguration, and under a circumstance where the number of symbolscontained in the UpPTS is larger than the preset threshold (or is thespecific special subframe configuration), the UpPTS and the uplinksubframes all can be used as the uplink transmission positions, orotherwise, only the uplink subframes can be used as the uplinktransmission position. For example, only when the number of uplinksubframes is not enough, the UpPTS can be used for UCI transmission. Forexample, in the LTE uplink and downlink configurations 2 and 4, there isonly one uplink subframe and one special subframe every 10 ms or 5 ms.In this case, one UCI transmission occupies one UpPTS and one uplinksubframe, totally 5 (or 6)+14=19 (or 20) symbols, used for one UCItransmission. To improve the coverage, retransmission may be performedbased on this.

Or, in Approach 5, when there are two continuous uplink subframes or aneven number of continuous uplink subframes, no matter how many symbolsin the UpPTS, only the uplink subframe U can be used as the uplinktransmission position to transmit UCI. For example, the uplink controlinformation 2 in FIG. 5 is only transmitted on two continuous uplinksubframes, and thus the integrity of UCI transmission can be ensured.For example, in an FDD NB-IoT system, the length of one RU in the PUSCHformat 2 having a subcarrier gap of 15 kHz is 2 ms. In this case, if theUCI needs repetition, then it will be transmitted in next two continuousuplink subframes, and the situation where only 1 uplink subframe leftwill not occur. In this way, it is convenience for the base station toperform scheduling. When there are not two or an even number ofcontinuous uplink subframes, an uplink transmission position may bedetermined according to the Approach 2 or the Approach 3. Specifically,for a subcarrier gap of 3.75 kHz, the length of one slot is 2 ms, andtherefore, for some uplink/downlink configurations, there may be 3uplink subframes, i.e., 3 ms, and in this case, the UE can only transmitone slot, i.e., 2 ms, and the third slot is idle and will not performany transmission. The next slot is transmitted next when there is acontinuous 2 ms uplink position.

Or, the base station may directly configure whether the UpPTS in thespecial subframe can be used for UCI transmission. Or the base stationmay configure a valid uplink transmission position by way of bitmap, andif the special subframe is configured as the valid uplink transmissionposition, then the UpPTS in the special subframe can be used for UCItransmission, and if the special subframe is configured as the invaliduplink transmission position, then the UCI can only be transmitted in anuplink subframe, and cannot be transmitted in the UpPTS of the specialsubframe.

The above approaches for indicating the UCI scheduling delay is alsoapplicable to indicate PDSCH and PUSCH. To be specific, the end positionof the PDCCH and the starting position of PDSCH or PUSCH which the PDCCHschedules is the first subframe that can be used for uplink or downlinktransmission after the scheduling delay indicated by the DCI.

In the following, several methods for determining the relativefrequency-domain position occupied by the UCI in step 403 will bedescribed.

FIG. 8 is a schematic diagram of a method for indicating afrequency-domain position for transmitting UCI information. After the UEdetermines the carrier for UCI transmission, the UE may divide severalsubcarriers in the carrier into several frequency-domain resources sets.As shown in FIG. 8, 12 subcarriers are divided into 4 frequency-domainresource sets, and the base station may configure one of the 4frequency-domain resource sets for the UE through RRC signaling or MACsignaling. Afterwards, the base station may further dynamically indicatea specific carrier from the set configured through DCI that indicatesPDSCH information. For example, in the DCI, using 2 bits indicatesposition 1 from the 3 positions, and then the UE transmits the UCI on asubcarrier 1 of the carrier for UCI transmission. Similarly, 12subcarriers may be divided into 3 or 2 frequency-domain resource sets,and there are 4 or 6 subcarriers in each frequency-domain resource set.In another example, the base station may configure the starting positionof a subcarrier, and then indicates an offset from its starting positionin DCI. For example, 2 bits may be used to indicate 4 offsets of {0, 1,2, 3}. Different UEs may obtain a starting subcarrier position or afrequency-domain resource set used for UCI transmission according toUE-specific RRC or MAC signaling. From the base station point of view,the base station may configure different frequency-domain positions forUEs having different number of repetitions, and in this way, it iseasier for the base station to schedule resources.

Specifically, the time-domain resource position and the frequency-domainresource position may be jointly indicated in DCI.

FIG. 9 is a detailed flowchart of a method for transmitting uplinkcontrol information according to an embodiment of the presentdisclosure.

Referring to FIG. 9, in step 901, a UE obtains configuration informationof a carrier for UCI transmission from a base station.

In step 903, the UE obtains a frequency-domain set or a frequency-domainstarting position for UCI transmission from an RRC message or MACinformation.

In step 905, the UE generates UCI information, and determining atime-frequency resource position for UCI transmission according to acorresponding downlink data channel or control channel and an uplinksubframe that is used for UCI transmission.

In step 704, the UE transmits the UCI information on the time-frequencyresource position of the UCI.

Specifically, a carrier used for transmitting HARQ-ACK feedbackinformation of MSG4 and/or a frequency-domain resource set in thecarrier may be broadcasted in system information (SIB). To be specific,one carrier and/or one frequency-domain resource set in the carrier maybe configured for each coverage level. In another example, the HARQ-ACKfeedback information of MSG4 is transmitted on a carrier where an NPRACHof a corresponding coverage level is located. In the TDD system, it maybe transmitted in an uplink subframe where the carrier for MSG4transmission is located. The carrier for transmitting the HARQ-ACKinformation of a downlink data channel after MSG4 and/or thefrequency-domain resource set in the carrier may be configured throughUE-specific RRC or may be rewritten by MAC signaling. If no carrier forUCI is configured, then in default, the UCI will be transmitted on acorresponding uplink carrier. In other words, transmission on anon-anchor carrier or a UCI-specific carrier may be enabled or disabledthrough configuration.

What described in the foregoing is a detailed implementation of themethod for transmitting UCI according to the present disclosure. Thepresent disclosure further provides a method for receiving UCI, and thereceiving method corresponds to the transmitting method.

Referring to FIG. 10, in step 1001, a base station determines at leasttwo carriers for uplink transmission allocated for a UE in a cellcurrently connected by the UE, and determines a carrier for UCItransmission of the UE from the at least two carriers for uplinktransmission;

In step 1003, the base station determines a relative frequency-domainposition and a time-domain starting position occupied by the UCI on thecarrier determined for UCI transmission;

In step 1005, the base station receives the UCI, on the carrier for UCItransmission of the UE, according to the relative frequency-domainposition and the time-domain starting position occupied by the UCI.

FIG. 11 is a schematic diagram illustrating a base station schedules theUCI of multiple UEs. As shown in FIG. 11, a carrier for UCI transmissionmay be configured by a cell-specific parameter or a user-specificparameter. From the base station point of view, the UCI of multipleusers may be transmitted on a same carrier. In addition, with theassistance of TDD uplink and downlink subframes, it is very easy toalign UCI transmission. To be specific, as shown in FIG. 11, PDSCH 1 andPDCCH 1 of UE1 are transmitted on carrier 1, PDSCH 2 and PDCCH 2 of UE2are transmitted on carrier 3, and however, the base station configuresthe UCI of UE1 and UE2 on carrier 2. In addition, it is easy to transmitthe UCI of two UEs in a same subframe according to an offset of timescheduling and an offset of frequency scheduling. In this way, thesegmentation of resources caused by UCI transmission may be avoided tothe maximum extent, so as to improve the spectral efficiency.

FIG. 12 is a schematic diagram illustrating a base station schedulesmultiple downlink transmissions for a UE. As shown in FIG. 12, the UEsupports 2 HARQ procedures, i.e., the UE can transmit the second HARQprocedure even if the first HARQ procedure is not completed. To bespecific, PDCCH1 schedules PDSCH1, and indicates UCI time offset 1;PDCCH 2 schedules PDSCH2, and indicates UCI time offset 2. By adjustingthe UCI time offset, two UCI can be transmitted in a same subframe. Inthis situation, they may be transmitted through HARQ bundling, i.e.,performing an “or” operation for the two HARQ situations to obtain abundling result, and then transmitting the bundling result. In anotherexample, as shown in FIG. 12, HARQ procedures may be transmitted ondifferent frequency-domain resources, to reduce PAPR, and twofrequency-domain resources for UCI transmission may occupy two adjacentsubcarriers. The base station may ensure the transmission by scheduling.

In addition, taking a situation where UCI and PUSCH may collide intoconsideration, the UCI may be transmitted on the PUSCH by means ofpiggyback. For example, as that in LTE, several symbols close to theDMRS are transmitted. Or the UCI may be transmitted on one subcarrier ofthe resources where the PUSCH is transmitted. The situation where theUCI and the PUSCH may collide may be a complete collision (including asituation where transmission times of them are equal or one of thetransmission times is larger than the other) or a partial collision (apart of them collides). As shown in FIG. 13, when the UCI transmissionand the PUSCH collide, the UCI may be transmitted on a subcarrierposition indicated by the base station in carrier 1 where the PUSCH istransmitted, and the PUSCH may puncture resources occupied by the UCI(i.e., performing rate matching according to originally scheduledresources, but not performing transmission on the resources occupied bythe UCI), or perform rate matching (i.e., deducting the resourcesoccupied by the UCI, and then performing rate matching). For DMRS, itmay continue to use PUSCH, or may also perform the puncture. From the UEpoint of view, DMRS for PUSCH decoding can also be used for UCIdecoding. In another example, the MAC control element or the MAC headermay be defined as a part of data channel to transmit. In the case ofpartial collision, the collision part may be processed as above, and thenon-collision part will be transmitted as normal, or the UCI or PUSCH ofthe collision part is dropped, i.e., not transmitted. The above methodmay be configured by the base station or may be predefined.

The present disclosure further provides an apparatus for transmittingUCI, and the apparatus can implement the UCI transmitting method in FIG.14. FIG. 14 is a schematic diagram of a basic structure of thetransmitting apparatus. As shown in FIG. 14, the transmitting apparatusincludes: a carrier determination unit 1410, a frequency-domain andtime-domain determination unit 1020 and a transmission unit 1430.

The carrier determination unit 1410 is configured to determine at leasttwo carriers for uplink transmission in a cell currently connected, anddetermine a carrier for UCI transmission from the at least two carriersfor uplink transmission. The UCI and the uplink data of the UE may betransmitted on different carriers. The frequency-domain and time-domaindetermination unit 1420 is configured to be used by the UE to determinea relative frequency-domain position and a time-domain starting positionoccupied by the UCI from the carrier determined for UCI transmission.The transmission unit 1430 is configured to retune a center radiofrequency of the UE to a center frequency of the carrier for UCItransmission, and transmit the UCI according to the relativefrequency-domain position and the time-domain starting position occupiedby the UCI; the transmission unit 1430 transmits information on onecarrier at one moment.

The present disclosure further provides an apparatus for receiving UCI,and the apparatus can be used to implement the UCI receiving methoddescribed in the foregoing. FIG. 15 is a schematic diagram of a basicstructure of the receiving apparatus. As shown in FIG. 15, the receivingapparatus includes: a carrier determination unit 1510, afrequency-domain and time-domain determination unit 1520 and a receivingunit 1530.

The carrier determination unit 1510 is configured to determine at leasttwo carriers for uplink transmission allocated for a UE in a cellcurrently connected by the UE, and determine a carrier for the UE totransmit UCI from the at least two carriers for uplink transmission. TheUCI and uplink data of the UE are transmitted on different carriers. Thefrequency-domain and time-domain determination unit 1520 is configuredto determine the relative frequency-domain and time-domain startingposition occupied by the UCI on the carrier determined to transmit theUCI. The receiving unit 1530 is configured to receive the UCI on thecarrier used by the UE to transmit the UCI according to the relativefrequency-domain position and the time-domain starting position occupiedby the UCI; the UE transmits information on one carrier at one time.

The NB-IoT system in the TDD frequency band may have three operationmodes. The first one is a separate operation mode independent of atraditional network, i.e., a standalone operation mode; the second oneis operating in a guardband of the LTE system, i.e., guardband operationmode; and the third one is operating on any resource block in the LTEcarrier, i.e., operating in inband of the LTE system, i.e., inbandoperation mode. Since a channel raster for the NB-IoT UE to perform cellsearching is 100 kHz, and therefore, if the NB-IoT is operating in theguardband of the LTE system, the channel raster of its anchor carrier (acarrier that transmits a synchronization channel) needs to satisfy 100kHz.

In the NB-IoT system, to enable a UE with low complexity can providemore flexible work in the operation environment, for the LTE inbandoperation mode and the guardband operation mode, a frequency offset of+/−7.5 kHz or +/−2.5 kHz from the 100 kHz channel raster is allowable.Assuming that the LTE center frequency satisfies the channel raster of100 kHz, Table 1 lists NB-IoT guardband operation modes corresponding todifferent LTE system bandwidths. As shown in Table 1, it includes ananchor carrier frequency (from it, an offset between a frequency used asthe anchor carrier and the LTE center frequency can be known) in theNB-IoT system, the distance from the LTE carrier, and the number ofanchor carriers that can be used as non-anchor carriers in one guardbandand the number of valid uplink carriers on each guardband.

To better reduce the LTE outband leakage, it is better to select afrequency/carrier closest to the LTE and meeting the channel rasterrequirement, and select a frequency/carrier farther from the LTE as anon-anchor carrier. As shown in Table 1, for an LTE system having abandwidth of 5 MHz, the anchor carrier of it may be configured atFc+2392.5 or Fc-2392.5 kHz, where Fc is the center frequency of the LTEsystem, so as to ensure that it is as close to the LTE as much, and meetthe channel raster requirement. To be specific, the anchor carrier has adistance of 45 kHz, i.e., 3 subcarriers, from the LTE edge. In this way,interference among the OFDM carriers of the LTE system may beeffectively avoided. Similarly, a system bandwidth of 15 MHz also needsto reserve a frequency width of 3 subcarriers to deploy the anchorcarrier. For LTE systems of 10 MHz and 20 MHz, the first PRB outside ofthe system bandwidth can meet the channel raster requirement, andtherefore, the first PRB outside of the system bandwidth can be used asthe anchor carrier. Besides of the frequencies in Table 1 that satisfythe anchor carrier channel raster requirement, there are a lot ofothers. However, since the spectrums of the frequencies in Table 1 aremostly used, the non-anchor carriers that can be deployed of them arethe most.

In addition, Table 1 lists the numbers of valid uplink carriers on LTEsystem guardbands corresponding to different LTE system bandwidths.Compared to the number of downlink carriers that can be used foroperating, since the outband leakage of the UE cannot achieve anaccuracy as that at the base station, to satisfy the outband leakagerequirement of LTE system so as to avoid interference with othersystems, the most outside carrier counted from the LTE center frequencycannot be used to perform uplink transmission for the UE. Therefore, ifthe most outside carrier is used, then an uplink carrier at a differentfrequency needs to be configured to pair it.

TABLE 1 LTE system Bandwidth 5 MHz 10 MHz 15 MHz 20 MHz Anchor carrierFc + 2392.5/ Fc + 4597.5/ Fc + 6892.5/ Fc + 9097.5/ frequency [kHz] Fc −2392.5  Fc − 4597.5  Fc − 6892.5  Fc − 9097.5  Distance from 45 kHz 0kHz 45 kHz 0 kHz LTE carrier Number of 1 (anchor 2 (1 anchor 3 (1 anchor5 (1 anchor downlink carrier) carrier + 1 carrier + 2 carrier + 4carriers in each non-anchor non-anchor non-anchor guardband carrier)carriers) carriers) Number of valid 0 1 2 4 uplink carriers in eachguardband

In fact, not only for the TDD NB-IoT system, but also for other TDDnarrow band systems, when they are deployed, a narrowband system mayoperate on the guardband of a wideband system (i.e., the guardbandoperation mode) or a narrowband system may operate within the systembandwidth of a wideband system (i.e., the inband operation mode). Thepresent disclosure provides a method for transmitting signals, used todetermine the center frequency of a downlink carrier or an uplinkcarrier in the guardband operation mode or the inband operation mode ofthe TDD narrowband system, so as to accurately transmit the signals.

FIG. 16 is a basic flowchart of a method for transmitting signals in theguardband operation mode or the inband operation mode of the TDD system.

Referring to FIG. 16, in step 1601, a UE obtains a first carrier in theTDD narrowband system, where the first carrier is in a guardband orinband of a TDD wideband system.

The first carrier may be an uplink carrier or a downlink carrier. Whenthe first carrier is an uplink carrier, the second carrier is a downlinkcarrier corresponding to the uplink carrier; and when the first carrieris a downlink carrier, the second carrier is an uplink carriercorresponding to the downlink carrier.

In step 1603, the UE determines indication information of a secondcarrier corresponding to the first carrier obtained in step 1601,determines an offset between the first carrier and the second carrier inthe TDD narrowband system according to the indication information, andcalculate a center frequency of the second carrier corresponding to thefirst carrier obtained in step 1601 according to the offset.

Determining the indication information of the second carriercorresponding to the first carrier obtained in step 1601 means to, whenthe first carrier obtained in step 1601 is an uplink carrier, determinethe indication information of a downlink carrier corresponding to theuplink carrier obtained in step 1601; and when the first carrierobtained in step 1601 is a downlink carrier, determine the indicationinformation of an uplink carrier corresponding to the downlink carrierobtained in step 1601. Similarly, calculating the center frequency ofthe second carrier corresponding to the first carrier obtained in step1601 according to the offset means to, when the first carrier obtainedin step 1601 is an uplink carrier, determine the center frequency of adownlink carrier corresponding to the uplink carrier obtained in step1601; and when the first carrier obtained in step 1601 is a downlinkcarrier, determine the center frequency of an uplink carriercorresponding to the downlink carrier obtained in step 1601. The offsetbetween the first carrier and the second carrier is an offset betweenthe uplink carrier/downlink carrier and the downlink carrier/uplinkcarrier.

In step 1605, the UE receives or transmits signals according to thecenter frequency of the second carrier determined in step 1603.

When the first carrier in step 1601 is a downlink carrier, the downlinkcarrier may be an anchor carrier or a non-anchor carrier.

In the following, the situation where what is obtained in step 1601 is adownlink carrier will be described.

When the downlink carrier in step 1601 is an anchor carrier, for a UEthat initially connects to/camps on the cell, the UE first performs cellsearching in step 1601 to obtain the center frequency of a downlinkanchor carrier A; then in step 1603, the UE obtains the indicationinformation of an uplink carrier corresponding to the downlink anchorcarrier A, and finally determines the center frequency of an uplinkcarrier B corresponding to the downlink anchor carrier. Or, when thedownlink carrier in step 1601 is a non-anchor carrier, same proceduresmay apply, which will not be elaborated herein.

To be specific, the UE may obtain the indication information throughhigher layer signaling (e.g., a master information block (MIB) or asystem information (SIB) or other RRC messages), and then determine thecenter frequency of the uplink carrier B corresponding to the downlinkcarrier A. Preferably, the indication information of the uplink carriermay be one piece of the following information: the absolute value of thecenter frequency of the uplink carrier, information of a positionrelative to the TDD wideband system, CRS sequence information. To bespecific, the offset from the center frequency of the downlink carriermay be a direction of frequency offset between the uplink and downlinkcarriers, or may be whether the uplink carrier is in the high frequencyor low frequency of the LTE system (left or right); the information ofthe uplink resources occupied by the uplink carrier B in the TDDwideband system may be the position (an index) of the PRB relative tothe LTE system; the position information of the uplink carrier; and theinformation of relative position in the TDD wideband system may be arelative position to the center frequency of the LTE, or a distance fromthe edge of the LTE system, or the nth carrier that can operate in theguardband, etc.

Further, a way of determining that the TDD narrowband system is locatedin the guardband or inband of the TDD wideband system in step 1601 maybe that the UE obtains the downlink carrier by performing cellsearching, and determines that the downlink carrier is in inband of thewideband system or in the guardband of the wideband system through thefollowing channel(s) or information: synchronization signal, MIB, SIB,UE-specific RRC signaling, physical layer indication information, andMAC layer indication information.

In the following, the detailed processing of step 1603 will bedescribed. As an example, the TDD narrowband system is a TDD NB-IoTsystem, the TDD wideband system is a TDD LTE system.

In Step 1603, the offset between the uplink frequency and downlinkfrequency in the TDD NB-IoT system needs to be determined according tothe indication information obtained. In the following, first the reasonthat there is an offset between the uplink and downlink carriers in theTDD NB-IoT system will be described.

In an LTE system, when dividing PRBs, among downlink carriers, a directsubcarrier (DC) does not belong to PRBs, but for the uplink direction,since a DC is on the center subcarrier, then the DC belongs to PRBs.Therefore, in the LTE system, uplink SC-FDMA and downlink OFDMA basebandsignal expressions are equivalent to a frequency-domain (phase) offsetof 7.5 kHz. As shown in FIG. 17, in the LTE system, subcarriers occupiedby downlink start from low frequency k=−└N_(RB) ^(DL)N_(sc) ^(RB)/2┘,skip k=0, and continue until k=┌N_(RB) ^(DL)N_(sc) ^(RB)/2┐. However,for the uplink direction, the LTE system occupies all subcarriers fromk=−└N_(RB) ^(DL)N_(sc) ^(RB)/2┘ to k=|N_(RB) ^(DL)N_(sc) ^(RB)/2|−1,where NR is the number of downlink PRBs, N_(RB) ^(UL) is the number ofuplink PRBs, N_(sc) ^(RB) is the number of subcarriers in one PRB, k isan index of frequency-domain in the OFDM or SC-FDMA system (for detailedinformation please refer to TS 36.211). For an NB-IoT system having theinband operation mode and the guardband operation mode, only a part ofthe bandwidth (e.g., a bandwidth of one PRB) of the LTE system isoccupied, and to prevent from the interference with the LTE system, theNB-IoT system needs to occupy downlink and uplink frequency-domainresources counted by the unit of PRB. Since uplink and downlink PRBs aredivided differently in the LTE system, in the TDD NB-IoT system havingthe inband operation mode and the guardband operation mode, there willbe a frequency offset of a half subcarrier bandwidth between a pair ofuplink and downlink center frequencies. For example, as shown by carrier1 and carrier 2 used in a narrowband system in FIG. 17, there is afrequency offset of +/−7.5 kHz between a frequency actually occupied byuplink and a frequency actually occupied by downlink in the TDD NB-IoTsystem. For a specific system (e.g., NB-IoT and LTE systems), theabsolute value of the uplink and downlink carrier offset is fixed (e.g.,for the NB-IoT system deployed in inband or a guardband of LTE system,the absolute value of the uplink and downlink carrier offset is 7.5kHz), and the UE may calculate it according to system parameters, or theabsolute value may be defined in a protocol, and then the signalingconfigures an offset to the left or to the right (positive or negativesign).

Based on the offset between the center frequencies of a pair of uplinkand downlink carriers in the NB-IoT system, for a TDD NB-IoT system thatoperates in inband or a guardband of the LTE TDD system, to avoid theinterference with the uplink and downlink transmission of the LTEsystem, in the present disclosure, the UE obtains the indicationinformation in step 1603, and uses the indication information tocalculate an offset between the center frequencies of the uplink anddownlink carriers, so as to accurately calculate the center frequency ofthe uplink carrier corresponding to the downlink carrier, based on thecenter frequency of the downlink carrier determined in step 1601, incombination with the offset between the center frequencies of the uplinkand downlink carriers. For the inband and guardband operation modes, thebase station may carry the indication information through an RRC message(including system information such as MIB, or SIB, or UE-specificmessage), and the indication information is used to calculate the offsetbetween the uplink and downlink carriers in the NB-IoT system.

FIG. 18 is an exemplary flowchart of a UE obtaining the center frequencyof an uplink carrier.

Referring to FIG. 18, in step 1801, the UE determines an operation modeof a TDD NB-IoT cell. In step 1803, the UE determines whether theoperation mode is an inband operation mode or a guardband operationmode, if the operation mode is neither of them, then performs step 1805;if the operation mode is one of them, then performs step 1807. In step1805, when the operation mode of the TDD NB-IoT cell is a standaloneoperation mode, the UE determines the center frequency of the uplinkcarrier is the center frequency of a downlink carrier corresponding tothe uplink carrier.

In step 1807, if the operation mode is the inband operation mode or theguardband operation mode, then the UE obtains indication information ofan uplink carrier corresponding to the downlink carrier, determines anoffset between the uplink and downlink carriers in the NB-IoT systemaccording to the indication information, and determines that the centerfrequency of the uplink carrier is the center frequency of the downlinkcarrier corresponding to the uplink carriers plus the offset.

The processing in step 1807 is equivalent to the processing in step1603. In step 1807, the offset between uplink and downlink carriers isdetermined according to an absolute value of the offset between uplinkand downlink carriers and an offset direction (i.e., a negative sign orpositive sign of the offset). The absolute value of the offset is fixed,and it is equal to the width of a half carrier of the NB-IoT system.Therefore, the uplink carrier indication information is mainly used todetermine the offset direction of the frequencies between the uplink anddownlink carriers. To be specific, the uplink carrier indicationinformation may be at least one piece of the following information: CRSsequence information, PRB indexes occupied by the uplink carrier, thedirection of a frequency offset between uplink and downlink carriers, arelative position to the LTE center frequency, a relative position tothe edge of the LTE system, nth carrier that can operate in theguardband, PRB positions (indexes) in the LTE, whether the uplinkcarrier is located in the high frequency of low frequency (left orright) of the LTE system. Herein, the offset between uplink and downlinkcarriers determined according to the indication information may be apositive number, a negative number, or zero. When the offset frequencyis zero, it means that the operation mode is the standalone operationmode.

In the above indication information, the frequency offset directionbetween uplink and downlink carriers is to indicate whether the offsetbetween uplink and downlink carriers is a positive number or a negativenumber, which is usually indicated using 1 bit. An uplink carrier islocated in the high frequency or low frequency (left or right) of theLTE system means that, in the guardband operation mode, the uplinkcarrier is located in a high frequency or low frequency (left or right)guardband of the LTE system; in the inband operation mode, it means thatthe uplink carrier is located in a high frequency or low frequency (leftor right) part of the LTE system. In fact, the parameter is also apositive sign or a negative sign indicating the offset between uplinkand downlink carriers.

Especially, if the higher layer configures that the operation mode isthe inband operation mode, and a same cell ID, then the UE may determinea CRS sequence and a channel raster offset according toeutra-CRS-SequenceInfo (CRS sequence information), as shown in Table 2.Table 2 provides LTE/(E-UTRA) PRB indexes n′_(PRB) and channel rasteroffset corresponding to each CRS sequence information. The LTE/(E-UTRA)PRB index n′_(PRB) is defined as n′_(PRB)=n_(PRB)−└N_(RB) ^(DL)/2┘. Inaddition, the offset between uplink and downlink center frequencies ofthe NB-IoT system may be deferred according to n′_(PRB). n′_(PRB) is theposition (sequence number) of a PRB relative to the LTE, n_(PRB) is theindexes of PRBs occupied by the uplink carrier, and when n′_(PRB) is apositive integer, the frequency offset of it is −7.5 kHz, and whenn′_(PRB) is a negative integer, the frequency offset is +7.5 kHz. Inthis case, the uplink carrier indication information may only includeCRS sequence information, it is not necessary to use additionalindication to determine the offset between uplink and downlink carriers.Its detailed implementation may be performed by adding an uplink anddownlink offset column to Table 2.

TABLE 2 E-UTRA E-UTRA PRB PRB index n′_(PRB) index _(n′) _(PRB) for oddfor even eutra-CRS- number of Raster eutra-CRS- number of RasterSequenceInfo N_(RB) ^(DL) offset SequenceInfo N_(RB) ^(DL) offset 0 −35−7.5 14 −46 +2.5 1 −30 kHz 15 −41 kHz 2 −25 16 −36 3 −20 17 −31 4 −15 18−26 5 −10 19 −21 6 −5 20 −16 7 5 +7.5 21 −11 8 10 kHz 22 −6 9 15 23 5−2.5 10 20 24 10 kHz 11 25 25 15 12 30 26 20 13 35 27 25 28 30 29 35 3040 31 45

In the case of inband operation mode with different cell IDs, or in thecase of guardband operation mode, 1 bit in MIB or SIB (e.g., SIB1, SIB2or SIB22) is used to indicate an uplink and downlink frequency offsetdirection, or indicate locating in a high frequency or low frequencypart of the LTE center frequency. Or, a relationship between n′_(PRB)and uplink and downlink frequency offset directions may be specified inthe protocol, and then an uplink and downlink frequency offset directionis determined according to n′_(PRB) in the uplink carrier indicationinformation, so as to further determine an uplink and downlink carrierfrequency offset. Similarly, for the guardband operation mode, MIB orSIM may be used to indicate at least one piece of the followinginformation: PRB index, or an offset between the carrier and the LTEcenter frequency, or whether an uplink carrier is located in the LTEhigh frequency or low frequency, or nth carrier that can operate in theguardband, and a distance from the LTE edge (e.g., the parameters inTable 1). In addition, the foregoing multiple information may be jointlycoded to use one index to indicate multiple information (e.g., LTEsystem bandwidth, uplink and downlink offset direction, located on thehigh frequency or the low frequency).

In addition, as shown in Table 1, for the guardband operation mode,since there are no uplink carriers to pair some carriers that can beused for downlink transmission, the base station may configure an uplinkcarrier for the UE to pair the carriers. The base station may configurethe uplink carrier pairing the downlink carriers for the UE through oneor more pieces of the following information: PRB index, PRB indexoffset, and absolute frequency offset. The configuration may beconfigured for the UE through RRC (including system information) or MACor physical layer indication or a combination of RRC and physical layer(PDCCH)/MAC layer. In addition, a specific uplink carrier may be definedfor a downlink carrier that does not have a paired uplink carrierthrough predefining, e.g., for example, defining that the specificuplink carrier is an uplink carrier corresponding to a neighboringdownlink carrier. When the base station configures carrier informationcorresponding to an unpaired downlink carrier, for the non-standaloneoperation mode, the base station may need to additionally configure anuplink and downlink frequency offset of the TDD narrowband system forthe UE, which may be carried out using the foregoing method, and willnot be elaborated herein.

Step 1603 is carried out through the foregoing processing, anddetermines the center frequency of the uplink carrier corresponding tothe downlink carrier. In the following, channel signals are transmittedon the determined uplink carrier.

What is described in the foregoing is detailed processing when what isobtained in step 1601 is a downlink carrier. When it is an uplinkcarrier that is obtained in step 1601, for example, the UE obtains anuplink carrier that is used to transmit random access channel (PRACH)through higher layer signaling (e.g., SIB 22), then indicationinformation of a downlink carrier corresponding to the uplink carrierobtained in step 1601 needs to be obtained in step 1603, and an uplinkand downlink carrier offset in the narrowband system is determinedaccording to the indication information, and then the center frequencyof the downlink carrier is calculated according to the offset. To bespecific, the content of the downlink carrier indication information issimilar to that of the indication information of the uplink carriermentioned in the foregoing, except that the uplink carrier is replacedwith downlink carrier, in which the definition of the CRS sequenceinformation is the same, as CRS is only present in the downlink.Similarly to the case of uplink carrier indication information, the UEfirst determines an uplink and downlink carrier frequency offsetdirection according to the uplink carrier indication information, andthen determines the offset between uplink and downlink carriers, plus anoffset based on the center frequency of the uplink carrier determined instep 1601 to obtain the center frequency of the downlink carrier. In thefollowing, the UE receives channel signals on the determined uplinkcarrier.

What is described in the foregoing is a detailed implementation of themethod for transmitting signals in the TDD narrowband system accordingto the present disclosure. The present disclosure further provides a UEin the TDD narrowband system, and the user equipment can be used toimplement the foregoing signal transmitting method. To be specific, theuser equipment includes an obtaining unit, a calculation unit, and atransmission unit.

The obtaining unit is configured to obtain an uplink or a downlinkcarrier of the TDD narrowband system. The calculating unit is configuredto, if the uplink or the downlink carrier obtained by the obtaining unitis determined to locate in inband or a guardband of a TDD widebandsystem, determine indication information of a downlink carrier or anuplink carrier corresponding to the uplink or the downlink carrierobtained by the obtaining unit, and determine an offset between theuplink/downlink carrier and the downlink/uplink carrier in the TDDnarrowband system according to the indication information, and calculatethe center frequency of the downlink or the uplink carrier correspondingto the uplink or the downlink carrier according to the offset and thecenter frequency of the uplink and downlink carriers. The transmissionunit is configured to transmit signals according to the center frequencyof the downlink or the uplink carrier calculated by the calculatingunit.

In an FDD NB-IoT system, NPRACH is transmitted on a single-subcarrierwith 3.75 kHz subcarrier spacing. In each NPRACH, one symbol groupconsists of one CP and five symbols, and every four symbol groups formone NPRACH transmission. In order to meet different levels of coverage,multiple repetitions can be configured for the NPRACH transmission.Frequency hopping is used between symbol groups, wherein the hoppingfrequency between the first and second symbol groups and between thethird and fourth symbol groups are 3.75 kHz, and the hopping frequencybetween the second and third symbol groups is 22.5 kHz. In order toreduce the inter-cell interference, pseudorandom frequency hopping ofLTE type 2 is used before every two repetitions.

The method and equipment for requesting random access of the presentdisclosure can be applied to radio communication systems based on TDD,especially to random access scenarios having an LTE TDD frame structure,an LTE TDD uplink-downlink configuration and a special time slotconfiguration.

FIG. 19 is a flowchart of a method for requesting random accessaccording to the present disclosure.

Referring to FIG. 19, in step 1901, a TDD uplink time-domain resource isdetermined. In step 1903, a time-domain resource used for transmitting anarrowband physical random access channel (NPRACH) is determinedaccording to the TDD uplink time-domain resource. In step 1905, atime-domain format for an NPRACH transmission group is determined, thetime-domain format comprising, one NPRACH transmission group comprisesat least two transmission units which are discontinuous in time domain,and one transmission unit comprises one or more NPRACH symbol groupswhich are continuous in time domain. In step 1907, an NPRACHtransmission group in the time-domain format is transmitted in thedetermined time-domain resource used for transmitting an NPRACH

FIG. 20 is a flowchart of a method for predicting a random access timingadvance (TA) according to the present disclosure. Referring to FIG. 20,in order to receive and detect NPRACH, a base station needs to receiveand detect an NPRACH transmission group containing discontinuoustransmission units. The method comprises the following steps.

Referring to FIG. 20, in step 2001, an NPRACH transmission group isreceived, wherein one NPRACH transmission group comprises a number oftransmission units which are discontinuous in time domain, onetransmission unit comprises one or more NPRACH symbol groups which arecontinuous in time domain, and phases between two adjacent transmissionunits are continuous or the phases are fixed.

In step 2003, a phase deviation is determined according to atime-frequency interval and/or frequency-domain interval between anumber of pairs of adjacent transmission units in the NPRACHtransmission group, and a timing advance (TA) is determined according tothe phase deviation. In step 2005, the TA is transmitted to indicate aUE to adjust a time-domain position for transmitting an NPRACHtransmission unit.

I. Acquisition of TDD Uplink Time-Domain Resource

The uplink time-domain resource can be one or more continuoustime-domain sections reserved for uplink transmission within a certainperiod of time. One continuous time-domain section is a combination of anumber of time units without any interval therebetween, and the timeunits can be subframes, time slots, symbols or more.

If the base station configures valid uplink subframe(s), the configuredvalid uplink subframe(s) is(are) used as TDD uplink time-domainresource.

If the base station configures valid downlink subframe(s), a subframeother than the configured valid downlink subframe(s) is(are) used as TDDuplink time-domain resource (in this case, no special subframe isconfigured).

If the base station configures an uplink-downlink configuration, anuplink subframe and an uplink pilot time slot (UpPTS) indicated by theuplink-downlink configuration information are used as TDD uplinktime-domain resource. Table 3 shows examples of the uplink-downlinkconfiguration information in LTE. As shown in Table 3, for subframes ineach system frame, “D” donates a downlink subframe reserved for downlinktransmission, “U” donates an uplink subframe reserved for uplinktransmission, and “S” donates a special subframe with three fields: adownlink pilot time slot (DwPTS) reserved for downlink transmission, aguard period (GP) and an uplink pilot time slot (UpPTS) reserved foruplink transmission. The length of the DwPTS and the length of the UpPTScan be additionally configured by a signaling, for example, by a specialsubframe.

The base station can perform the configuration by a radio resourcecontrol (RRC) message, including a system message, a dedicated RRCconfiguration or more. In another example, the base station configuresor rewrites a semi-static RRC configuration by a physical layer(layer 1) signaling, for example, DCI. In another example, the basestation configures or rewrites the configuration by an MAC signaling,for example, MAC control elements (CEs), MAC protocol data units (PDUs)or more.

Specifically, the valid uplink or downlink subframe(s) can be configuredby a bitmap. For example, 10 or 40 bits indicate 10 or 40 time units(for example, subframes, time slots, symbols or more), respectively. Inthe method of configuring by a bitmap, a special subframe can beinserted according to a predefined rule, for example, the subframe usedfor downlink-to-uplink conversion is defined as a special subframe. Inthe method of configuring by a bitmap, the special subframe can betemporarily considered as the last downlink subframe, or not consideredas an uplink or downlink subframe, or can be considered as the firstuplink subframe. Or, only when the guard period between the valid uplinksubframe and the valid downlink subframe is less than a certain value, aGP is created, for example, by puncturing or skip several uplink ordownlink symbols. In another example, uplink subframes can be configuredby configuring the ratio between uplink subframe(s) and downlinksubframe(s), for example, 1:1, 1:4 or more. The way of configuringuplink subframes by configuring the ratio between uplink subframe(s) anddownlink subframe(s) can also be combined with a configured orpredefining a period, where the ratio represents the proportion ofuplink and downlink subframes within this period. During the calculationof the ratio, the special subframe can be temporarily considered as anuplink or downlink subframe.

For different frequency-band deployment modes, for example, LTE in-banddeployment, LTE guard-band deployment and stand-alone deployment, theconfiguration can be performed by different methods. For example, withregard to the LTE in-band or guard-band deployment, it is moreappropriate to directly follow the uplink-downlink configuration for theLTE to avoid the interference to the LTE system. However, with regard tothe stand-alone deployment, the configuration can be done by configuringvalid uplink or downlink subframes or by configuring the ratio.

In addition, the base station can broadcast a cell-specificuplink-downlink configuration by an SIB broadcast. The base station canalso reconfigure a UE-specific uplink-downlink configuration by adedicated RRC signaling, an Mac signaling or a physical layer channel.

In addition, for a PUSCH or a PUCCH, uplink subframes can be dynamicallydetermined according to the scheduling. For example, a UE transmits anuplink channel in PUSCH or PUCCH on time-frequency resources dynamicallyindicated by a physical layer. In this case, it is unnecessary toacquire the TDD uplink time-domain resource. That is, on the UE side,there is no need to distinguish a TDD system or an FDD system.

TABLE 3 Uplink-downlink configurations in LTE Uplink- Downlink- downlinkto-uplink config- switching Subframe No. uration point period 0 1 2 3 45 6 7 8 9 0  5 ms D S U U U D S U U U 1  5 ms D S U U D D S U U D 2  5ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D DD D D 5 10 ms D S U D D D D D D D 6  5 ms D S U U U D S U U D

II. Format for the NPRACH Symbol Group

The format for the NPRACH symbol group comprises a time-frequencyformat. A time-domain format and a frequency-domain format in thetime-frequency format will be described below.

In an FDD NB-IoT system, a physical layer random access preamble isbased on single-subcarrier frequency hopping symbol groups. A randomaccess preamble sequence group consists of four symbol groups, and thefour symbol groups are transmitted for N_rep{circumflex over ( )}NPRACHtimes without gaps. One symbol group consists of a cyclic prefix (CP) oflength of TCP and 5 identical symbols with total length of TSEQ, whereinthe parameters are as shown in Table 4. Ts is a time unit, and satisfiesthe condition: 30720·T_S=1 ms. In the FDD NB-IoT system, the NPRACHtransmission starts from N_start{circumflex over ( )}NPRACH·30720T_stime units after the starting position of a system frame satisfying thecondition n_f mod(N_start{circumflex over ( )}NPRACH/10).N_start{circumflex over ( )}NPRACH is the starting time of the NPRACH,N_period{circumflex over ( )}NPRACH is the period of NPRACH resources,and both N_start{circumflex over ( )}NPRACH and N_period{circumflex over( )}NPRACH are configured by the base station through an RRC (SIB).

TABLE 4 Random access preamble parameters for FDD Preamble sequenceformat T_(CP) T_(SEQ) 0 2048T_(s) 5 · 8192T_(s) 1 8192T_(s) 5 ·8192T_(s)

Since there are no continuous uplink subframes with a length of severalmilliseconds in a TDD system, particularly when in the LTE in-banddeployment and the LTE guard-band deployment, the design in the FDDNB-IoT system cannot be reused. In order to enable one symbol group ofthe NPRACH to be transmitted within a time-domain range of one UpPTSplus one uplink subframe, the number of symbols and/or the length of theCP in the NPRACH symbol group is to be reduced. Specific examples referto Table 5.

TABLE 5 Random access preamble parameters for TDD T_(CP) T_(SEQ) A14480T_(s) 3 · 8192T_(s) A2 2048T_(s) 4 · 8192T_(s) A3 1480T_(s) 4 ·8192T_(s) A4 2576T_(s) 4 · 8192T_(s) A5  672T_(s) 5 · 8192T_(s) A61768T_(s) 5 · 8192T_(s)

Table 5 shows examples of random access preamble parameters for TDD.

A1: a symbol group consisting of a CP with a length of 4480 Ts and threesymbols at a subcarrier spacing of 3.75 kHz.

A2: a symbol group consisting of a CP with a length of 2048 Ts and foursymbols at a subcarrier spacing of 3.75 kHz.

A3: a symbol group consisting of a CP with a length of 1480 Ts and foursymbols at a subcarrier spacing of 3.75 kHz.

A4: a symbol group consisting of a CP with a length of 2576TS and foursymbols at a subcarrier spacing of 3.75 kHz.

A5: a symbol group consisting of a CP with a length of 2576 Ts and fivesymbols at a subcarrier spacing of 3.75 kHz.

A6: a symbol group consisting of a CP with a length of 672 Ts and fivesymbols at a subcarrier spacing of 3.75 kHz.

By comparing Table 4 with Table 5, relative to FDD, one symbol group inthe TDD time-domain format comprises one CP and three to five symbols,and the total length of each symbol group is not greater than 43008*Ts(the length of TCP+TSEQ in the preamble sequence format 0 in Table 4).That is, the total length of a single symbol group is reduced.

If other subcarrier spacings are used, the symbol length will changecorrespondingly. For example, at a subcarrier spacing of 15 kHz, thesymbol length is 2048 Ts. If the number of symbols in one symbol groupremains unchanged, nearly ¼ Ts is correspondingly reduced. However, inorder to support a certain cell coverage radius, the length of the CPshould be approximate to but less than 2048 Ts. In other words, withregard to a subcarrier length of 15 kHz, one symbol group comprises oneCP and three to six symbols, and the total length of each symbol groupis not greater than 14336 Ts (one CP with a length of 2048 Ts and sixsymbols each with a length of 2048 Ts). The number of symbols can bedetermined according to the length of the NPRACH transmission units andthe number of symbol groups in each transmission unit. If a subcarrierspacing of 15 kHz or more is used, the number of symbol groups in eachtransmission unit should be more than 2, for example, 2 or 4, so that asufficient frequency-hopping interval can be provided for eachtransmission unit to realize accurate TA estimation.

It is to be noted that, in the above examples, a GP (guard period) canbe created at the end of a symbol group by further importing a TA. Theabove examples are applicable to different special subframeconfigurations. Specifically, for example:

an UpPTS of one symbol plus an uplink subframe: A1, A2, A3 and A4;

an UpPTS of two symbols plus an uplink subframe: A2, A3 and A4;

an UpPTS of three symbols plus an uplink subframe: A2, A3 and A4;

an UpPTS of four symbols plus an uplink subframe: A2, A4 and A5;

an UpPTS of five symbols plus an uplink subframe: A2, A4, A5 and A6; and

an UpPTS of six symbols plus an uplink subframe: A6 or the NPRACH format0 in the FDD NB-IoT.

Notes: In the latter three situations, A1 and A3 can also be selected,but the GP will be far longer than the CP, resulting in waste.

In addition, a subcarrier spacing of 15 kHz can also be designed. Thus,15 symbols can be contained in an uplink subframe of 1 ms. One symbolcan be used as a CP. Or, a half (1024 Ts) of a symbol is used as a CP,and the other half is used as a GP. In a case of a special subframe plusan uplink subframe, like 3.75 kHz, approximately one symbol or a half ofa symbol is selected as a CP, and other symbols are used to transmitNPRACH symbols.

In addition, in order to adapt to the transmission in the above formatand reserve a GP equivalent to the CP in length, different timingadvances need to be imported. That is, the actual transmission time ofthe NPRACH occupies more uplink symbols or is advanced by more timeunits than other uplink transmission channels or signals. Or, the actualtransmission time of the NPRACH is advanced by more time units than theuplink transmission in the LTE system. For a random access channel, anadditional TA will not influence base stations (BS) or terminals in thesystem. Since the GP in the TDD system design is used to ensure that, inan actual system, a terminal that is located at the cell edge andrequires a larger TA will not interfere, when using a larger TAconfiguration, the reception of downlink subframe(s) by this UE.However, since, in the NB-IoT system, uplink scheduling and downlinkscheduling can ensure a GP of 1 ms, the terminal will not be influencedeven if an additional TA is provided to the NPRACH. The specificconfiguration of the TA, the reference time or more will be descriedbelow in detail.

III. NPRACH Transmission

The format for an NPRACH transmission group will be described first. Thetime-domain format for the NPRACH transmission group can be determinedaccording to at least one of following parameters: the uplinkconfiguration, the special subframe configuration, the NPRACH formatconfiguration, and the deployment mode.

In order to use uplink subframe(s) having a limited continuous length ora combination of uplink subframe(s) and an UpPTS in a TDD system,multiple symbol groups can be divided into a number of transmissionunits, and these transmission units are transmitted discontinuously inthe time domain. That is, a guard time is inserted between twotransmission units. One transmission unit comprises one or more symbolgroups which are continuous in time domain. A UE transmits an NPRACH inunit of transmission groups, where each transmission group comprises anumber of transmission units. That is, the UE transmits one transmissiongroup during each transmission of the NPRACH. FIG. 21 is a schematicdiagram of an NPRACH transmission group. As shown in FIG. 21, one NPRACHtransmission group comprises a number of transmission units 2121, 2122and 2123, and the transmission units are transmitted discontinuously inNPRACH uplink resources 2101, 2102 and 2103, respectively. Eachtransmission unit comprises two symbol groups. For example, thetransmission unit 2121 comprises two symbol groups 2111 and 2112; thetransmission unit 2122 comprises two symbol groups 2113 and 2114; andthe transmission unit 2123 comprises two symbol groups 2115 and 2116.After each transmission unit, a certain time interval is reserved as aguard period (GP), for example, GPs 2131, 2132 and 2133. Preferably,each transmission group comprises two transmission units or threetransmission units. The length of one NPRACH symbol group or the numberof symbols in the symbol group is directly configured by the UEaccording to the RRC, or determined according to the special subframeconfiguration and uplink-downlink configuration of the cell. That is,the UE determines the NPRACH time-frequency format according to at leastone of the following information: the received RRC signaling, specialsubframe configuration information and uplink-downlink configurationinformation. Between different symbol groups, the frequency hopping isused for timing estimation. As shown in FIG. 21, same or differentfrequency-hopping intervals can be used between the symbol groups 2111and 2112, between the symbol groups 2113 and 2114, and between thesymbol groups 2115 and 2116. That is, each symbol is transmitted on adifferent frequency-domain resource. Preferably, the one or morefrequency-hopping intervals between symbol groups in a number oftransmission units in one NPRACH transmission group are different.

The BS estimates a TA according to a phase deviation between symbolgroups transmitted on different frequency-domain resources. By importingdifferent frequency-hopping intervals between NPRACH transmissiongroups, both the estimation accuracy of the TA and the supported cellradius can be improved. The BS calculates a phase deviation resultedfrom different time-domain positions occupied by the continuouslytransmitted symbol groups in each transmission unit, and then estimatesthe TA based on the phase deviation. Or, the BS also estimates the TA,according to different frequency-domain intervals occupied by symbolgroups between different discontinuously transmitted transmission units.In order to estimate the TA by the frequency-hopping interval betweenthe discontinuously transmitted symbol groups, the UE needs to ensurethat the phase at the end of the previous symbol group is the same asthe phase at the beginning of the next symbol group (the phases arecontinuous) or that the phase at the end of the previous symbol groupand the phase at the beginning of the next symbol group satisfy a fixedphase deviation.

For example, the BS continuously receives a first NPRACH transmissionunit, and then receives a second NPRACH transmission unit after acertain time interval X. The BS determines, according to the firstNPRACH transmission unit, the second NPRACH transmission unit and thecertain time interval X, a TA for the UE to transmit the NPRACHtransmission units. Further, the BS determines, according to thefrequency-hopping interval(s) between multiple symbol groups in theNPRACH transmission units and the time interval X, a phase deviationbetween symbols, and then determines a TA according to the phasedeviation. Preferably, the phases of the two transmission units arecontinuous or are fixed values.

Further, in order to increase the NPRACH coverage, the UE can repeatedlytransmit the NPRACH transmission group for multiple times. Specifically,the UE can determine the repetition times N for transmissions of theNPRACH transmission group and then repeatedly transmit, on thedetermined TDD uplink time-domain resource, the NPRACH transmissiongroup with the time-domain format for N times. Preferably, the BSconfigures one or more NPRACH resources, and each NPRACH resourcecorresponds to a different repetition times N. Thus, the UE selects,according to the coverage level where the UE is located, a correspondingNPRACH resource to request random access.

Referring to FIG. 22, it is a schematic diagram of one transmission ofan NPRACH by a UE, i.e., transmission of one transmission group. Forexample, within two system frames (20 ms), four transmission units aretransmitted for four times. One transmission unit is transmitted in anUpPTS in a special subframe and an uplink subframe following the UpPTSevery 5 ms. In the example of FIG. 22, each transmission unit comprisesone symbol group, that is, each transmission unit consists of one CP anda number of symbols. For example, each transmission unit consists of oneCP and three, four or five symbols. The transmissions of eachtransmission units are discontinuous. Moreover, since each transmissionunit is followed by a downlink subframe or an uplink subframe used forother channels or other UEs' uplink transmission, a GP is needed aftereach discontinuously transmission unit to avoid the inter-symbolinterference. In FIG. 22, one transmission unit comprises one symbolgroup. That is, the first symbol group, the second symbol group, thethird symbol group and the fourth symbol group are not transmittedcontinuously, and a GP is inserted after each symbol group to avoidinterference. The uplink-downlink configuration in FIG. 22 is theuplink-downlink configuration 2 in Table 3, and one transmission of theNPRACH containing four symbol groups will take 20 ms. If theuplink-downlink configuration 5 in Table 3 is used or otheruplink-downlink configurations (e.g., configuration 3 or configuration4) at a switching period of 10 ms are used, one transmission of theNPRACH containing four symbol groups will take 40 ms. For theconfiguration 3 or configuration 4, or for the configuration 0,configuration 1 or configuration 6 among the uplink-downlinkconfigurations, two symbol groups can be continuously transmitted in twoor three continuous uplink subframes, so that the transmission delay isreduced.

Referring to FIG. 23, it is a schematic diagram of one transmission ofan NPRACH by a UE, i.e., transmission of one transmission group. In FIG.23, one transmission unit comprises two NPRACH symbol groups which aretransmitted continuously, which occupies one UpPTS in a special subframeand three uplink subframes after the UpPTS; and, a GP is needed afterone transmission unit (i.e., two NPRACH symbol groups) to avoid theinter-symbol interference. Specifically, as shown in FIG. 21, a GP isinserted after the second symbol group and the fourth symbol group,respectively. In addition, one or two NPRACH symbol groups can alsooccupy one UpPTS and two subsequent uplink subframes. The UE candetermine the transmission mode of the NPRACH according to theuplink-downlink configuration and the special subframe configuration,for example, the number of the continuously transmitted symbol groups inone transmission unit. During one NPRACH transmission, the number ofsymbol groups in each transmission unit can be the same or different.For example, in the uplink-downlink configuration 9, one UpPTS and threeuplink subframes are continuously transmitted within first 5 ms, and oneUpPTS and two uplink subframes are continuously transmitted withinlatter 5 ms. In this case, the number of the continuously transmittedsymbol groups in one transmission unit can be different.

In the embodiments shown in FIG. 22 and FIG. 23, no matter whether thesymbol groups are continuous or not, different symbol groups aretransmitted with frequency hopping. For example, a firstfrequency-hopping interval is used between the first and second symbolgroups; and similarly, the first frequency-hopping interval is also usedbetween the third and fourth symbol groups. A second frequency-hoppinginterval is used between the second and third symbol groups. Forexample, the first frequency-hopping interval can be an NPRACHsubcarrier spacing. The first frequency-hopping interval is 3.75 kHz,and the second frequency-hopping interval is 22.5 kHz. The firstfrequency-hopping interval, the second frequency-hopping interval andother frequency-hopping intervals can be adjusted to other valuesaccording to the subcarrier spacing, the cell radius, the multi-carrierconfiguration or other factors. For example, the secondfrequency-hopping interval can be greater than the width of one carrier.In addition, four symbol groups in FIG. 22 or FIG. 23 are used as onefrequency-hopping pattern unit. When four symbol groups in a nextfrequency-hopping pattern unit are transmitted, a thirdfrequency-hopping interval is used between the fourth symbol group andthe first symbol group in the next unit. The third frequency-hoppinginterval can also be greater than the width of one carrier. Similarly,for an NPRACH channel at a subcarrier spacing of 15 kHz, frequencyhopping can be performed at 3.75 kHz to maintain the estimation accuracyof the TA, or frequency hopping is performed at 15 kHz to maintain theintegrity of the system. The second frequency-hopping interval can befrequency hopping at 150 kHz or 120 kHz. Thus, the NPRACH channel can belocated at two frequency-domain edges of one carrier (PRB), while theinterior of this carrier is reserved for NPUSCH transmission. If thesymbols of the NPRACH are at a subcarrier spacing of 15 kHz, the lengthof the symbols is ¼ of 3.5 kHz, and the total number of symbols in onesymbol group in the foregoing embodiments can be increased by 4 times.Or, in the same continuous uplink resource, there can be two to foursymbol groups in one NPRACH transmission unit. Thus, in one transmissionunit, two or more frequency-hopping intervals can be provided toaccurately estimate the TA and support a larger cell radius.

As shown in FIG. 22 and FIG. 23, the BS calculates, according to thepredefined first frequency-hopping interval between the first and secondsymbol groups and between the third and fourth symbol groups and thepredefined second frequency-hopping interval between the second andthird symbol groups, a phase deviation resulted from the TA, andestimates the TA according to the phase deviation and the first andsecond frequency-hopping intervals. The frequency hopping between thefirst and second symbol groups and the frequency hopping between thethird and fourth symbol groups can be inverse, for example, 3.5 kHz and−3.75 kHz. In the TDD system, one NPRACH transmission group consists ofdiscontinuously transmitted transmission units. Therefore, during thecalculation of the phase deviation, the time interval X fordiscontinuous transmissions will be taken into consideration. Inaddition, when the TA is estimated by the phase deviation resulted fromthe frequency hopping between discontinuous transmissions, it will beensured that the phases are continuous or the phase deviation ispre-known.

In addition, in order to meet higher coverage requirements, the NPRACHtransmission group can be repeated for multiple times. The BS canconfigure the starting position of the repetition of the NPRACHtransmission group and the repetition times. The third frequency-hoppinginterval is used between different repetitions of the NPRACHtransmission group. In order to adapt to different coverage levels, theNPRACH can be configured with one or more levels, wherein each levelcorresponds to different repetition times of the transmission group. Indifferent coverage levels, the time-domain format for the NPRACHtransmission group can be the same or different. In addition, in orderto offload the number of UEs, the NPRACH can be configured in multiplecarriers, for example, non-anchor carriers, wherein the non-anchorcarriers are carriers in which no synchronization signal is transmitted.Different transmission group formats, different repetition times or morecan be configured for NPRACH in different carriers. For example,different non-anchor carriers are deployed in different deploymentmodes, for example, LTE in-band deployment, LTE guard-band deployment orstand-alone deployment.

In one example, a terminal acquires, according to the uplink subframeconfiguration, an uplink-downlink switching period to transmitdiscontinuously transmitted NPRACH resources. For example, regardless ofthe uplink subframe configuration, i.e., no matter how many uplinksubframes, one or more continuously transmitted symbol groups in theNPRACH start from the uplink-downlink switching period.

In one example, the UE determines, according to the distribution ofuplink subframes and special subframes, the starting position of thefirst symbol group of each transmission unit, or determines, accordingto the number of uplink subframe(s) on a continuous uplink time-domainsection for one transmission unit, the starting position of the firstsymbol group of this transmission unit.

Referring to FIG. 24, in the example of FIG. 24, each NPRACH symbolgroup merely occupies one special subframe and one uplink subframe. Evenif there are three continuous uplink subframes transmitted in the uplinksubframe configuration, the NPRACH will not continuously occupy theremaining continuous uplink subframe(s). Thus, these subframes can beused for other uplink channels, for example, a transmission of a NPUSCH.

In one example, a terminal determines a time interval (including astarting time interval between first symbol groups of the two continuoustransmission units, or a time interval between the end of the lastsymbol group of the previous transmission unit and the head of the firstsymbol group of the next transmission unit, or in other ways ofdetermining the time interval between two transmission units) betweentwo continuous transmission units by receiving RRC direct configurationinformation from a BS. As shown in FIG. 23, the BS can directlyconfigure the period between NPRACH symbol groups as 10 ms through theRCC. In addition, one or more NPRACH formats can be defined, and eachformat predefines a corresponding time interval value used fordetermining the time-domain interval between two continuous transmissionunits, so that the terminal can determine the time-domain intervalbetween two transmission units according to the NPRACH time-frequencyformat and the predefined corresponding value.

Further, in order to use a same NPRACH format as far as possible in thecase of different uplink-downlink subframe configurations or specialsubframe configurations, the starting position of one or more symbolgroups in the NPRACH and the period can be directly configured throughthe RRC (as shown in FIG. 24, the period of the NPRACH transmissionunits can be configured). For example, an offset of one or more systemframes from a certain reference point is directly configured through theRRC. The reference point can be the starting position of a certainsubframe. The offset is used for determining the time-domain startingposition of one or more symbol groups (i.e., transmission units) in oneNPRACH transmission. As shown in FIG. 24, an offset 1 from the startingposition of a subframe 0 or an offset 2 from the starting position of aspecial subframe (a subframe 1) can be configured. Thus, regardless ofthe uplink subframe configuration, the presence or absence of thespecial subframe, and the special subframe configuration, the NPRACH canbe configured in a same way. In different deployment modes, a sameconfiguration method can be used. It is easily understood that thereference point can also be an uplink subframe, a downlink subframe, asystem frame, or even a symbol in a subframe, or more, and a terminaldetermines the reference point by TDD uplink time-domain resource. Theoffset can also be a predetermined fixed value.

The frequency-domain position for NPRACH transmission will be describedbelow. A UE determines a frequency-domain position for transmittingdifferent NPRACH symbol groups (i.e., determines at least one of acarrier position, a subcarrier group and a subcarrier position)according to the received indication of an RRC signaling, apredetermined fixed value or a downlink control signaling, and thendetermines a range of frequency-domain resources for transmittingdifferent NPRACH symbol groups in a frequency hopping manner. In acontention-based random access process, the UE selects a subcarrier froma subcarrier group for transmission, and transmits several symbol groupsin a frequency hopping manner according to a specified frequency-hoppingpattern. In a scheduling-based random access process, the UE transmitsan NPRACH according to a subcarrier configured by a BS. Preferably, thefrequency-hopping pattern can be predefined or determined by a cell IDor determined by a random sequence generated by using a cell ID as aseed. In addition, from the perspective of the BS, configuring differentcarriers or subcarriers (groups) for a NPRACH for different cells canprevent the long-term occupation of fixed uplink resources by the NPRACHfrom resulting in access delay or mismatch of uplink-downlink resources.In addition, the frequency hopping for the NPRACH can improve the NPRACHdetection performance and avoid the inter-cell interference.

IV. TA for the NPRACH

The coverage range of a cell is limited by a CP and a GP of an NPRACH.Therefore, a GP equivalent to the CP in length is to be inserted atleast after each continuous transmission. In the system design, theintegrity will be taken into consideration during the design of the CP,the GP and the length (number) of symbols in a symbol group. Forexample, in the design of one UpPTS plus one uplink subframe, in orderto ensure the orthogonality of a downlink subframe following the uplinksubframe or the data transmitted in the downlink subframe, the NPRACHcan be transmitted in advance relative to the downlink. Further, theNPRACH can be additionally transmitted in advance relative to otheruplinks. The UE can acquire the TA through one or more of the followingconfigurations: the RRC signaling which indicates that the transmissiontime for the NPRACH is ahead by m time units (before the correspondingresource for UL transmission), the special subframe configuration, theTDD uplink-downlink configuration, the deployment mode, the preset TAvalue corresponding to the NPRACH format, the predefined fixed TA ormore.

FIG. 22 and FIG. 23 show examples of acquiring the TA by the UE throughthe RRC signaling which indicates that the transmission time for theNPRACH is ahead by m time units (before the corresponding resource forUL transmission). Relative to the starting position of the UpPTS, theNPRACH is transmitted by additionally advancing by m time units (i.e.,the TA value). This is done for the purpose that a GP equivalent to theCP in length can be obtained after the continuous uplink transmission.

Examples of acquiring, by the UE, the TA according to the specialsubframe configuration and the NPRACH format will be described below.Table 6 shows embodiments of the special subframe configuration. X canbe configured to 2 or 4 by an RRC parameter in an SIB, so that theutilization rate of special subframes is increased. A GP with a lengthof at least one symbol needs to be ensured.

TABLE 6 Special subframe configuration in case of a normal CP Specialsubframe configuration DwPTS UpPTS 0  6592 · T_(s) (1 + X) · 2192 ·T_(s) 1 19760 · T_(s) 2 21952 · T_(s) 3 24144 · T_(s) 4 26336 · T_(s) 5 6592 · T_(s) (2 + X) · 2192 · T_(s) 6 19760 · T_(s) 7 21952 · T_(s) 824144 · T_(s) 9 13168 · T_(s) 10 13168 · T_(s)      13152 · T_(s)

Specifically, with regard to several NPRACH formats in Table 5 and thenumber of symbols in different UpPTSs:

(1) An UpPTS of one symbol plus one uplink subframe: for example,special subframe configurations 0 to 4 in Table 6, and X=0.

With regard to A1 in Table 5, a GP of 4480Ts can be obtained only by afixed TA NTA of 624 Ts for TDD, like the LTE, so that a cell radiusapproximate to 22 km is provided.

With regard to A2 in Table 5, the fixed TA for the NPRACH is to beadjusted from 62 Ts to NTA=2816 Ts, or an additional TA offset NTAoffsetof 2192 Ts is added for the NPRACH, so that a cell radius approximate to7.2 km can be provided.

With regard to A3 in Table 5, NTA=5008 Ts is to be set or NTAoffset=4384Ts is to be additionally added, so that a cell radium of 12.5 km isprovided.

With regard to A4 in Table 5, NTA=3952 Ts is to be set or NTAoffset=3328Ts is to be additionally added.

(2) An UpPTS of two symbols plus one uplink subframe: for example,special subframe configurations 5, 6, 7, 8 and 9 in Table 6, and X=0.

Like A2 and A4 in the case of one symbol, 2*2192 Ts can be subtractedfrom the corresponding TA. With regard to A3, NTA=624 Ts can be directlyused.

(3) An UpPTS of three symbols plus one uplink subframe: for example,special subframe configurations 0, 1 and 2 in Table 6, and X=2.

With regard to A2, A3 and A4, no additional TA is required. With regardto A3, the GP will be greater than the CP.

(4) An UpPTS of four symbols plus one uplink subframe: for example,special subframe configurations 5, 6 and 9 in Table 6, and X=2.

With regard to A2 and A4, the transmission can be performed directly,without needing an additional TA, or even NTA can be set as 0, i.e.,NTA=0. With regard to A5, NTA=624 Ts can be used, and cells having acell radius less than 3.3 km can be supported.

(5) An UpPTS of five symbols plus one uplink subframe: for example,special subframe configuration 0 in Table 6, and X=4.

With regard to A2, A4 and A5, the transmission can be performeddirectly. Or, with regard to A2, the fixed TA for the NPRACH is to beadjusted from 624 Ts to NTA=1184 Ts; or, by adding an additional TAoffset NTAoffset of 560 Ts to the NPRACH, a cell radius approximate to10 km can be provided.

(6) An UpPTS of six symbols plus one uplink subframe: for example,special subframe configurations 5 and 9 in Table 4, and X=0; or, thespecial subframe configuration 10.

A6 can be transmitted directly by a fixed TA of 624 Ts, and a cellradius of 8.6 km can be provided.

Or, for the transmission of the NPRACH format 0 in the FDD NB-IoT, thefixed TA for the NPRACH is to be adjusted from 624 Ts to NTA=1184 Ts;or, by adding an additional TA offset NTAoffset of 560 Ts to the NPRACH,a cell radius approximate to 10 km can be provided.

Several time-frequency formats for the NPRACH transmission group havebeen provided above based on the subcarrier spacing of 3.75 kHz. Thenumber of Ts for each symbol will change correspondingly if thesubcarrier spacing changes. The number of symbols in each symbol groupcan be calculated according to the number of Ts of the uplinktime-domain resource for the NPRACH and the number of symbol groups inthe corresponding transmission unit. Furthermore, the corresponding CP,GP, the required TA and the size of the supported cell radius arederived.

In addition, in the foregoing embodiments, the NPRACH transmission usesthe starting position of the UpPTS as a reference point, and the TA isdescribed relative to the starting position of the UpPTS. Essentially,the count of Ts starts from the starting position of each system frameor subframe. For a special subframe, the actual reference point is adownlink subframe/time slot. In addition, the BS can directly configurethe offset transmitted by the NPRACH (for example, through the RRC). TheUE determines the starting time to transmit the NPRACH according to theoffset. The reference time of the offset can be the starting position ofa certain uplink or downlink subframe, or the starting position of acertain system frame, or the starting position of a certain symbol in acertain subframe (for example, the position of the UpPTS) or more. Thereference time can be predefined in a protocol or configured by a BS(for example, RRC).

From the perspective of the system design, the protocol can define oneor more NRPACH formats applicable to the TDD system, and the BS candirectly configure an NPRACH format for a UE. Or, the UE determines anNPRACH format according to the special subframe configuration and/or theuplink-downlink configuration or more.

V. Calculation of RA-RNTI

In the process of interacting with a BS to complete random access, anRA-RANTI can be calculated by the UE according to one or more of thefollowing parameters: the NRPACH format, the hyper frame number, thesystem frame, subframes, the uplink-downlink configuration or more.Preferably, the RA-RNTI is calculated according to the switching timebetween UL and DL or the configuration period of valid UL and DLsubframes.

In Rel-13 and Rel-14 NB-IoT systems, the UE calculates the RA-RNTI inthe following way:

RA-RNTI = 1 + floor  (SFN_id/4) + 256 * carrier_id

where the Carrier-id denotes the ID (serial number) of a carrier, andSFN-id denotes the ID of a system frame. In an FDD system, the time totransmit one NPRACH is 5.6 ms or 6.4 ms. In a TDD system, due todiscontinuous uplink transmission, the time to transmit one NPRACHchannel is extended to 20 ms to 40 ms, according to different uplinksubframe configurations. With regard to different NPRACH periods orswitching periods of uplink and downlink subframes, different methodsfor calculating the RA-RNTI can be selected.

For example, with regard to the NPRACH symbol group transmission periodof 5 ms or the uplink-downlink switching period of 5 ms:

RA-RNTI = 1 + floor  (SFN_id/16) + 64 * carrier_id

With regard to the NPRACH symbol group transmission period of 10 ms orthe uplink-downlink switching period of 10 ms:

RA-RNTI = 1 + floor  (SFN_id/32) + 32 * carrier_id

In addition, if this adjustment is insufficient to meet the requirementson the RA-RNTI, the hyper frame number can be further imported in thecalculation of the RA-RNTI, for example:

RA-RNTI = 1 + floor  (SFN_id/64) + floor  (HFN_id/4) + 32 * carrier_id

where HFN-id is the ID of the hyper frame number.

In the TDD system, the UE can receive a downlink channel at an intervalof transmitting the NPRACH in an uplink subframe. In thecoverage-enhanced mode, the NPRACH needs to be repeatedly transmittedfor multiple times. The BS detects each NPRACH transmission to detectthe NPRACH and estimate a TA. For a UE under better channel conditions,the BS can successfully detect the NPRACH in advance and then obtain anaccurate TA estimation. In this case, the BS can transmit a RandomAccess Response (RAR) in advance. For example, the starting position ofan RAR window is defined on a downlink subframe before the repeatedlytransmitted NPRACH. In the process of transmitting the NPRACH, a TDD UEor a Full Duplex FDD (FD-FDD) UE can monitor an NPDCCH used forindicating the RAR. If the UE has successfully detected an NPDCCH inresponse to the RA-RNTI scrambling and has successfully decoded thecorresponding NPDSCH, the UE can stop transmitting the NPRACH inadvance. Thus, the uplink transmission time can be reduced, and thepower consumption of the UE is thus reduced.

VI. Transmission of Msg3 and Other Uplink Channels

In a TDD system, some uplink resources will be reserved for the NPRACHchannel. In order to avoid the collision of an uplink channel with anNPRACH, an Msg3 can be transmitted in a carrier the same as or differentfrom that for the NPRACH, wherein the position of the carrier which isused for transmitting the Msg3 is obtained by the RRC configuration fromthe BS, or predefined in the system, or indicated by an MAC CE (controlelement) (e.g., RAR). Similarly, other uplink channels can be scheduledto other uplink carriers for transmission through an RRC, an MAC or aDCI.

In addition, inter-carrier frequency hopping can be imported in thetransmission of uplink channels. In one example, when the scheduling ofthe NPUSCH collides with the NPRACH, the NPUSCH will be hopped toanother carrier. The another carrier is scheduled by an RRC. The NPUSCcomprises a format 1 for transmitting data and/or a format 2 or 3 fortransmitting uplink control information. If no additional carrier isconfigured, the transmission of the NPUSCH is postponed to a subsequentuplink subframe.

In addition, the timing relationship between the Msg3 and the RAR can bedefined to start from the first valid uplink subframe (including or notincluding a special subframe) after 12 ms.

FIG. 25 is a module diagram of a UE according to the present disclosure.Referring to FIG. 25, the UE includes an uplink resource determiningmodule 2510, a transmission resource determining module 2520, atransmission format determining module 2530, and an NPRACH transmissionmodule 2540.

The uplink resource determining module 2510 configured to determine aTime Division Duplex (TDD) uplink time-domain resource. The transmissionresource determining module 2520 configured to determine, according tothe TDD uplink time-domain resource, a time-domain resource used fortransmitting a narrowband physical random access channel (NPRACH). Thetransmission format determining module 2530 configured to determine atime-domain format for an NPRACH transmission group, the time-domainformat comprising: one NPRACH transmission group comprises a number oftransmission units which are discontinuous in time domain, and onetransmission unit comprises one or more NPRACH symbol groups which arecontinuous in time domain. The NPRACH transmission module configured totransmit, in the determined time-domain resource used for transmittingan NPRACH, an NPRACH transmission group in the time-domain format.

The operation processes of the uplink resource determining module, thetransmission resource determining module, the transmission formatdetermining module and the NPRACH transmission module correspond to thesteps 1901, 1903, 1905 and 1907 in the method for requesting randomaccess of the present disclosure, and will not be repeated here.

It can be seen from the detailed description of the present disclosurethat, compared with the prior art, the present disclosure has at leastthe following beneficial technical effects:

firstly, by designing a time-domain format for NPRACH transmissionaccording to the characteristics of TDD uplink time-domain resource, arandom access process can be deployed within an LTE band or an LTE guardband and applied to an NB-IoT communication system based on TDD, so thatthe existing NB-IoT based on FDD can be applicable to the operation modeof TDD. Accordingly, a higher utilization rate of spectrum resources isachieved, and the system throughput and connection efficiency of theNB-IoT system in a scenario where a large number of UEs are to beconnected are significantly improved;

secondly, by providing multiple methods for determining TDD uplinktime-domain resource and a time-domain transmission position of theNPRACH, and by configuring the starting position of the time-domaintransmission and the time-domain interval between transmission units bymultiple approaches, for example, by the RRC signaling, theuplink-downlink subframe configuration, the uplink-downlink switchingperiod or the NPRACH format, the application scenarios of the randomaccess method are enriched, and the expansibility of the system isincreased;

thirdly, by adding a timing advance before the time-domain position fortransmitting the NPRACH, the inter-symbol interference is greatlyreduced, the success probability of the random access is significantlyimproved, and the resource utilization and the random access performanceof the UE are optimized;

fourthly, by improving the structure and length of an existing NPRACHsymbol group to adapt to the frame structure and uplink-downlinkconfiguration in the TDD mode, the method is applicable to TDDcommunication systems; and meanwhile, by designing multiple NPRACHformats, the flexibility of the random access resource configuration isimproved, and the access efficiency is thus improved; and

fifthly, the base station estimates a TA according to the time-frequencyinterval and frequency-domain interval between adjacent transmissionunits in the NPRACH transmission group in the time-domain format andthen feeds back the TA to the UE, so that the accuracy of the TAestimation is greatly improved, and the success probability of therandom access is increased.

It should be understood by those skilled in the art that the presentdisclosure involves devices for carrying out one or more of operationsas described in the present disclosure. Those devices can be speciallydesigned and manufactured as intended, or can comprise well knowndevices in a general-purpose computer. Those devices have computerprograms stored therein, which are selectively activated orreconstructed. Such computer programs can be stored in device (such ascomputer) readable media or in any type of media suitable for storingelectronic instructions and respectively coupled to a bus, the computerreadable media include but are not limited to any type of disks(including floppy disks, hard disks, optical disks, CD-ROM and magnetooptical disks), Read-Only Memory (ROM), Random Access Memory (RAM),Erasable Programmable Read-Only Memory (EPROM), Electrically ErasableProgrammable Read-Only Memory (EEPROM), flash memories, magnetic cardsor optical line cards. In other words, the readable media comprise anymedia storing or transmitting information in a device (for example,computer) readable form.

It should be understood by those skilled in the art that computerprogram instructions can be used to realize each block in structurediagrams and/or block diagrams and/or flowcharts as well as acombination of blocks in the structure diagrams and/or block diagramsand/or flowcharts. It should be understood by those skilled in the artthat these computer program instructions can be provided to generalpurpose computers, special purpose computers or other processors ofprogrammable data processing means to be implemented, so that solutionsdesignated in a block or blocks of the structure diagrams and/or blockdiagrams and/or flow diagrams disclosed by the present disclosure areexecuted by computers or other processors of programmable dataprocessing means.

It should be understood by those skilled in the art that the steps,measures and solutions in the operations, methods and flows alreadydiscussed in the present disclosure can be alternated, changed, combinedor deleted. Further, other steps, measures and solutions in theoperations, methods and flows already discussed in the presentdisclosure can also be alternated, changed, rearranged, decomposed,combined or deleted. Further, the steps, measures and solutions of theprior art in the operations, methods and operations disclosed in thepresent disclosure can also be alternated, changed, rearranged,decomposed, combined or deleted.

The foregoing descriptions are merely some implementations of thepresent disclosure. It should be noted that, to a person of ordinaryskill in the art, various improvements and modifications can be madewithout departing from the principle of the present disclosure, andthese improvements and modifications shall be regarded as falling intothe protection scope of the present disclosure.

1. A method performed by a user equipment (UE) in a wirelesscommunication system, the method comprising: receiving, from a basestation via a radio resource control (RRC) signaling, system informationblock (SIB) for two uplink carriers in one cell, wherein the two uplinkcarriers include: a first uplink carrier corresponding to a downlinkcarrier in which a downlink synchronization signal is received, and asecond uplink carrier different from the first uplink carrier; andtransmitting, to the base station, an uplink signal on one of the twouplink carriers configured to the UE, wherein, in case of a frequencydivision duplex (FDD) system, the SIB includes first information forindicating a carrier position of the first uplink carrier, wherein, incase of a time division duplex (TDD) system, a center frequency of thefirst uplink carrier and a center frequency of the downlink carrier aresame and the SIB does not include the first information for indicatingthe carrier position of the first uplink carrier, and wherein the SIBincludes second information for indicating a carrier position of thesecond uplink carrier.
 2. The method of claim 1, wherein an uplinktransmission slot of the uplink signal is identified according to a timeoffset indicated by downlink control information (DCI) received from thebase station.
 3. The method of claim 1, wherein a frequency-domainresource of the uplink signal is indicated from a frequency-domainresource set, by downlink control information (DCI) for physicaldownlink shared channel (PDSCH) received from the base station, andwherein the frequency-domain resource set is configured for one of thetwo uplink carriers configured to the UE, through a radio resourcecontrol (RRC) signaling.
 4. The method of claim 3, wherein the uplinksignal comprises at least one of hybrid automatic repeatrequest—acknowledge (HARQ-ACK) information, scheduling request (SR)information, or channel state information (CSI).
 5. The method of claim1, wherein the transmitting of the uplink signal comprises: in case thatthe uplink signal includes a hybrid automatic repeat requestacknowledgement (HARQ-ACK) feedback of a physical downlink sharedchannel (PDSCH) associated with a message 4 (MSG 4) of a random accessprocedure, identifying the one of the two uplink carriers, which is usedfor physical random-access channel (PRACH) transmission of therandom-access procedure.
 6. A method performed by a base station in awireless communication system, the method comprising: transmitting, to auser equipment (UE) via a radio resource control (RRC) signaling, systeminformation block (SIB) for two uplink carriers in one cell, wherein thetwo uplink carriers include: a first uplink carrier corresponding to adownlink carrier in which a downlink synchronization signal istransmitted, and a second uplink carrier different from the first uplinkcarrier, and receiving, from the UE, an uplink signal on one of the twouplink carriers configured to the UE, wherein, in case of a frequencydivision duplex (FDD) system, the SIB includes first information forindicating a carrier position of the first uplink carrier, wherein, incase of a time division duplex (TDD) system, a center frequency of thefirst uplink carrier and a center frequency of the downlink carrier aresame and the SIB does not include the first information for indicatingthe carrier position of the first uplink carrier, and wherein the SIBincludes second information for indicating a carrier position of thesecond uplink carrier.
 7. The method of claim 6, wherein an uplinktransmission slot of the uplink signal is associated with a time offsetindicated by downlink control information (DCI) transmitted to the UE.8. The method of claim 6, wherein a frequency-domain resource of theuplink signal is indicated from a frequency-domain resource set, bydownlink control information (DCI) for physical downlink shared channel(PDSCH) transmitted to the UE, and wherein the frequency-domain resourceset is configured for one of the two uplink carriers configured to theUE, through a radio resource control (RRC) signaling.
 9. The method ofclaim 8, wherein the uplink signal comprises at least one of hybridautomatic repeat request—acknowledge (HARQ-ACK) information, schedulingrequest (SR) information, or channel state information (CSI).
 10. Themethod of claim 6, wherein, in case that the uplink signal includes ahybrid automatic repeat request acknowledgement (HARQ-ACK) feedback of aphysical downlink shared channel (PDSCH) associated with a message 4(MSG 4) of a random access procedure, the one of the two uplinkcarriers, which is used for physical random-access channel (PRACH)transmission of the random-access procedure, is configured for theuplink signal.
 11. A user equipment (UE) in a wireless communicationsystem, the UE comprising: a transceiver; and at least one processorcoupled with the transceiver, configured to: receive, from a basestation via a radio resource control (RRC) signaling, system informationblock (SIB) for two uplink carriers in one cell, wherein the two uplinkcarriers include: a first uplink carrier corresponding to a downlinkcarrier in which a downlink synchronization signal is received, and asecond uplink carrier different from the first uplink carrier, andtransmit, to the base station, an uplink signal on one of the two uplinkcarriers configured to the UE, wherein, in case of a frequency divisionduplex (FDD) system, the SIB includes first information for indicating acarrier position of the first uplink carrier, wherein, in case of a timedivision duplex (TDD) system, a center frequency of the first uplinkcarrier and a center frequency of the downlink carrier are same and theSIB does not include the first information for indicating the carrierposition of the first uplink carrier, and wherein the SIB includessecond information for indicating a carrier position of the seconduplink carrier.
 12. The UE of claim 11, wherein an uplink transmissionslot of the uplink signal is identified according to a time offsetindicated by downlink control information (DCI) received from the basestation.
 13. The UE of claim 11, wherein a frequency-domain resource ofthe uplink signal is indicated from a frequency-domain resource set, bydownlink control information (DCI) for physical downlink shared channel(PDSCH) received from the base station, and wherein the frequency-domainresource set is configured for one of the two uplink carriers configuredto the UE, through a radio resource control (RRC) signaling.
 14. The UEof claim 13, wherein the uplink signal comprises at least one of hybridautomatic repeat request—acknowledge (HARQ-ACK) information, schedulingrequest (SR) information, or channel state information (CSI).
 15. The UEof claim 11, wherein the at least one processor, to transmit the uplinksignal, is configured to: in case that the uplink signal includes ahybrid automatic repeat request acknowledgement (HARQ-ACK) feedback of aphysical downlink shared channel (PDSCH) associated with a message 4(MSG 4) of a random access procedure, identify the one of the two uplinkcarriers, which is used for physical random-access channel (PRACH)transmission of the random-access procedure.
 16. A base station in awireless communication system, the base station comprising: atransceiver; and at least one processor coupled with the transceiver,configured to: transmit, to a user equipment (UE) via a radio resourcecontrol (RRC) signaling, system information block (SIB) for two uplinkcarriers in one cell, wherein the two uplink carriers include: a firstuplink carrier corresponding to a downlink carrier in which a downlinksynchronization signal is transmitted, and a second uplink carrierdifferent from the first uplink carrier, and receive, from the UE, anuplink signal on one of the two uplink carriers configured to the UE,wherein, in case of a frequency division duplex (FDD) system, the SIBincludes first information for indicating a carrier position of thefirst uplink carrier, wherein, in case of a time division duplex (TDD)system, a center frequency of the first uplink carrier and a centerfrequency of the downlink carrier are same and the SIB does not includethe first information for indicating the carrier position of the firstuplink carrier, and wherein the SIB includes second information forindicating a carrier position of the second uplink carrier.
 17. The basestation of claim 16, wherein an uplink transmission slot of the uplinksignal is associated with a time offset indicated by downlink controlinformation (DCI) transmitted to the UE.
 18. The base station of claim16, wherein a frequency-domain resource of the uplink signal isindicated from a frequency-domain resource set, by downlink controlinformation (DCI) for physical downlink shared channel (PDSCH)transmitted to the UE, and wherein the frequency-domain resource set isconfigured for one of the two uplink carriers configured to the UE,through a radio resource control (RRC) signaling.
 19. The base stationof claim 18, wherein the uplink signal comprises at least one of hybridautomatic repeat request—acknowledge (HARQ-ACK) information, schedulingrequest (SR) information, or channel state information (CSI).
 20. Thebase station of claim 16, wherein, in case that the uplink signalincludes a hybrid automatic repeat request acknowledgement (HARQ-ACK)feedback of a physical downlink shared channel (PDSCH) associated with amessage 4 (MSG 4) of a random access procedure, the one of the twouplink carriers, which is used for physical random-access channel(PRACH) transmission of the random-access procedure, is configured forthe uplink signal.